Deploy Steam builds to Shinespark beta

## Summary

- stack residual airborne knockback per axis after the configured launch-frame threshold
- apply DI after combining the launch vectors while retaining the second hit's hitstun
- preserve and decay residual knockback after hitstun
- make stacking state rollback-safe and include it in debug save states
- clear launch state on landing, ledge interactions, KO, and respawn

## Testing

- `cargo check --tests`
- `cargo test` (159 tests passed)
- `git diff --check`

## Asset configuration

For Melee timing, `knockback_stacking_window` should be set to `10`. The local ignored asset package has been updated accordingly.

Reviewed-on: #97
Co-authored-by: Álex Román Núñez <eirexe@eirteam.moe>

.gitea/workflows/ci.yml

@@ -211,8 +211,8 @@ jobs:
           username: ${{ secrets.STEAM_USERNAME }}
           password: ${{ secrets.STEAM_PASSWORD }}
           totp: ${{ steps.steam-totp.outputs.code }}
-          appId: 3409670
+          appId: 1216230
           buildDescription: ${{ github.sha }}
           rootPath: build
           depot1Path: game
-          releaseBranch: master
+          releaseBranch: shinespark

Cargo.toml

@@ -45,11 +45,6 @@ fixed_math = "0.4.1"
 [profile.dev.package."*"]
 opt-level = 3
 
-# The rollback simulation runs multiple times per rendered frame in sync-test
-# mode, so optimizing the game crate is important even for development builds.
-[profile.dev]
-opt-level = 1
-
 [profile.production]
 inherits = "release"
 lto = "thin"

src/debug_tools.rs

@@ -116,6 +116,7 @@ enum DebugFlag {
     AttackHitboxes,
     Hurtboxes,
     Camera,
+    LedgeGrab,
     DrawThroughGeometry,
     FrameStepping,
 }
@@ -164,6 +165,10 @@ const FIGHTER_MENU: &[DebugMenuEntry] = &[
         label: "Attack hitboxes",
         flag: DebugFlag::AttackHitboxes,
     },
+    DebugMenuEntry::Toggle {
+        label: "Ledge grab",
+        flag: DebugFlag::LedgeGrab,
+    },
     DebugMenuEntry::Toggle {
         label: "Hurtboxes",
         flag: DebugFlag::Hurtboxes,
@@ -260,6 +265,7 @@ pub struct DebugSettings {
     pub attack_hitboxes: bool,
     pub hurtboxes: bool,
     pub camera: bool,
+    pub ledge_grab: bool,
     pub draw_through_geometry: bool,
     pub motion_sampling: PresentationMotionMode,
     pub game_speed: GameSpeedDebug,
@@ -283,6 +289,7 @@ impl Default for DebugSettings {
             attack_hitboxes: false,
             hurtboxes: false,
             camera: false,
+            ledge_grab: false,
             draw_through_geometry: false,
             motion_sampling: PresentationMotionMode::default(),
             game_speed: GameSpeedDebug::Full,
@@ -350,6 +357,7 @@ impl DebugSettings {
             DebugFlag::Hurtboxes => self.hurtboxes,
             DebugFlag::DrawThroughGeometry => self.draw_through_geometry,
             DebugFlag::Camera => self.camera,
+            DebugFlag::LedgeGrab => self.ledge_grab,
             DebugFlag::FrameStepping => self.frame_stepping,
         }
     }
@@ -368,6 +376,7 @@ impl DebugSettings {
                 self.draw_through_geometry = !self.draw_through_geometry
             }
             DebugFlag::Camera => self.camera = !self.camera,
+            DebugFlag::LedgeGrab => self.ledge_grab = !self.ledge_grab,
             DebugFlag::FrameStepping => self.frame_stepping = !self.frame_stepping,
         }
     }
@@ -926,6 +935,10 @@ pub fn camera_debug_enabled(settings: Res<DebugSettings>) -> bool {
     settings.camera
 }
 
+pub fn ledge_grab_enabled(settings: Res<DebugSettings>) -> bool {
+    settings.ledge_grab
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;

src/debug_tools/save_state.rs

@@ -1,12 +1,26 @@
 use bevy::prelude::*;
 
 use crate::{
-    camera::MatchCamera, fighter::{
+    camera::MatchCamera,
-        FighterECB, FighterFacingDirection, FighterHitboxes, FighterHitstop, FighterHitstopShake, FighterInvulnerabilityState, FighterPendingRespawn, FighterPreviousFacingDirection, FighterPreviousTranslation, FighterSurfaceState, FighterTranslation, FighterVelocity, animation::FighterAnimationFrame, attack::{
+    fighter::{
-            FighterDamage, FighterKnockbackVelocity, FighterPendingHitReaction, FighterPendingHits,
+        FighterECB, FighterFacingDirection, FighterHitboxes, FighterHitstop, FighterHitstopShake,
-            FighterSolvedHurtboxes, FighterStaleMoveQueue,
+        FighterInvulnerabilityState, FighterLedgeInformation, FighterPendingRespawn,
-        }, baked_animation::FighterBoneMatrices, state::FighterState,
+        FighterPreviousFacingDirection, FighterPreviousTranslation, FighterSurfaceState,
-    }, input::FighterInput, match_runtime::MatchState, player::Player, stage::line::StageCollision,
+        FighterTranslation, FighterVelocity,
+        animation::FighterAnimationFrame,
+        attack::{
+            FighterDamage, FighterKnockbackState, FighterKnockbackVelocity,
+            FighterPendingHitReaction, FighterPendingHits, FighterSolvedHurtboxes,
+            FighterStaleMoveQueue,
+        },
+        baked_animation::FighterBoneMatrices,
+        ecb::FighterDesiredECB,
+        state::FighterState,
+    },
+    input::FighterInput,
+    match_runtime::MatchState,
+    player::Player,
+    stage::line::StageCollision,
 };
 
 #[derive(Resource, Default)]
@@ -27,6 +41,7 @@ struct FighterCheckpoint {
     entity: Entity,
     handle: usize,
     ecb: FighterECB,
+    desired_ecb: FighterDesiredECB,
     previous_ecb: crate::fighter::ecb::FighterPreviousECB,
     velocity: FighterVelocity,
     translation: FighterTranslation,
@@ -41,6 +56,7 @@ struct FighterCheckpoint {
     hitstop: FighterHitstop,
     hitstop_shake: FighterHitstopShake,
     knockback_velocity: FighterKnockbackVelocity,
+    knockback_state: FighterKnockbackState,
     stale_moves: FighterStaleMoveQueue,
     hitboxes: FighterHitboxes,
     solved_hurtboxes: FighterSolvedHurtboxes,
@@ -48,6 +64,7 @@ struct FighterCheckpoint {
     surface: FighterSurfaceState,
     pending_respawn: FighterPendingRespawn,
     invulnerability_state: FighterInvulnerabilityState,
+    ledge_information: FighterLedgeInformation,
 }
 
 pub(super) fn save_or_restore(world: &mut World) {
@@ -130,6 +147,7 @@ pub(super) fn save_or_restore(world: &mut World) {
 
         let mut entity = world.entity_mut(saved.entity);
         entity.insert(saved.ecb);
+        entity.insert(saved.desired_ecb);
         entity.insert(saved.previous_ecb);
         entity.insert(saved.velocity);
         entity.insert(saved.translation);
@@ -144,6 +162,7 @@ pub(super) fn save_or_restore(world: &mut World) {
         entity.insert(saved.hitstop);
         entity.insert(saved.hitstop_shake);
         entity.insert(saved.knockback_velocity);
+        entity.insert(saved.knockback_state);
         entity.insert(saved.stale_moves.clone());
         entity.insert(saved.hitboxes.clone());
         entity.insert(saved.solved_hurtboxes.clone());
@@ -151,6 +170,7 @@ pub(super) fn save_or_restore(world: &mut World) {
         entity.insert(saved.surface.clone());
         entity.insert(saved.pending_respawn.clone());
         entity.insert(saved.invulnerability_state.clone());
+        entity.insert(saved.ledge_information.clone());
     }
     world.insert_resource(checkpoint.pending_hits.clone());
     world.insert_resource(checkpoint.stage_collision);
@@ -167,6 +187,7 @@ fn capture_fighter(world: &World, entity: Entity) -> Option<FighterCheckpoint> {
         entity,
         handle: fighter.get::<Player>()?.handle,
         ecb: *fighter.get::<FighterECB>()?,
+        desired_ecb: *fighter.get::<FighterDesiredECB>()?,
         previous_ecb: *fighter.get::<crate::fighter::ecb::FighterPreviousECB>()?,
         velocity: *fighter.get::<FighterVelocity>()?,
         translation: *fighter.get::<FighterTranslation>()?,
@@ -181,6 +202,7 @@ fn capture_fighter(world: &World, entity: Entity) -> Option<FighterCheckpoint> {
         hitstop: *fighter.get::<FighterHitstop>()?,
         hitstop_shake: *fighter.get::<FighterHitstopShake>()?,
         knockback_velocity: *fighter.get::<FighterKnockbackVelocity>()?,
+        knockback_state: *fighter.get::<FighterKnockbackState>()?,
         stale_moves: fighter.get::<FighterStaleMoveQueue>()?.clone(),
         hitboxes: fighter.get::<FighterHitboxes>()?.clone(),
         solved_hurtboxes: fighter.get::<FighterSolvedHurtboxes>()?.clone(),
@@ -188,6 +210,7 @@ fn capture_fighter(world: &World, entity: Entity) -> Option<FighterCheckpoint> {
         surface: fighter.get::<FighterSurfaceState>()?.clone(),
         pending_respawn: fighter.get::<FighterPendingRespawn>()?.clone(),
         invulnerability_state: fighter.get::<FighterInvulnerabilityState>()?.clone(),
+        ledge_information: fighter.get::<FighterLedgeInformation>()?.clone(),
     })
 }
 

src/fighter/animation.rs

@@ -87,6 +87,10 @@ pub enum AnimKind {
     CrouchEnter,
     CrouchIdle,
     CrouchExit,
+    LedgeWait,
+    LedgeJump,
+    LedgeGetUp,
+    LedgeGrab,
 
     PlatformPass,
 
@@ -100,6 +104,7 @@ pub enum AnimKind {
     AttackDownTilt,
     AttackNeutralAir,
     AttackForwardAir,
+    AttackDownAir,
     AttackDash,
     AttackUpSmash,
 }

src/fighter/attack/directional_influence.rs

@@ -15,6 +15,16 @@ pub fn apply_directional_influence(
     let (sin, cos) = attack_angle.sin_cos();
     let base_launch_direction = FGVec2::new(cos, sin);
 
+    apply_directional_influence_to_direction(receiver_stick, base_launch_direction, di_max_angle)
+}
+
+/// Applies DI to an already-computed launch direction. This is used after
+/// knockback stacking, where the resulting angle may differ from either hit.
+pub fn apply_directional_influence_to_direction(
+    receiver_stick: FGVec2,
+    base_launch_direction: FGVec2,
+    di_max_angle: FGi32,
+) -> FGVec2 {
     let Some(base_launch_direction) = base_launch_direction.normalize() else {
         return FGVec2::ZERO;
     };
@@ -30,14 +40,20 @@ pub fn apply_directional_influence(
         -di_max_angle.to_fixed::<FGWide>(),
         di_max_angle.to_fixed::<FGWide>(),
     );
-    let (sin, cos) = (attack_angle + angle_change.to_fixed::<FGi32>()).sin_cos();
+    let (sin, cos) = angle_change.to_fixed::<FGi32>().sin_cos();
-    FGVec2::new(cos, sin).normalize_or_zero()
+    FGVec2::new(
+        base_launch_direction.x * cos - base_launch_direction.y * sin,
+        base_launch_direction.x * sin + base_launch_direction.y * cos,
+    )
+    .normalize_or_zero()
 }
 
 #[cfg(test)]
 mod test {
     use crate::{
-        fighter::attack::directional_influence::apply_directional_influence,
+        fighter::attack::directional_influence::{
+            apply_directional_influence, apply_directional_influence_to_direction,
+        },
         math::{int::FGi32, vec::FGVec2},
     };
 
@@ -66,4 +82,17 @@ mod test {
         assert!(di.x > FGi32::ZERO);
         assert!(di.y < FGi32::ZERO);
     }
+
+    #[test]
+    fn vector_di_preserves_a_stacked_direction_without_input() {
+        let direction = FGVec2::lit("-0.6", "0.8");
+        let result = apply_directional_influence_to_direction(
+            FGVec2::ZERO,
+            direction,
+            FGi32::lit("18.0"),
+        );
+        const EPSILON: FGi32 = FGi32::from_bits(6);
+        assert!(result.x.abs_diff(direction.x) < EPSILON);
+        assert!(result.y.abs_diff(direction.y) < EPSILON);
+    }
 }

src/fighter/attack/mod.rs

@@ -33,6 +33,75 @@ use crate::{
 #[derive(Deref, Component, Default, Hash, Debug, Copy, Clone)]
 pub struct FighterKnockbackVelocity(pub FGVec2);
 
+/// Lifecycle state for the currently active launch velocity.
+///
+/// This counts frames where knockback was actually applied to movement; hitstop
+/// therefore does not advance it. Melee uses this age to decide whether a
+/// subsequent airborne hit replaces or stacks with the previous launch.
+#[derive(Component, Default, Hash, Debug, Copy, Clone)]
+pub struct FighterKnockbackState {
+    pub frames_since_launch: u32,
+}
+
+impl FighterKnockbackState {
+    pub fn restart(&mut self) {
+        self.frames_since_launch = 0;
+    }
+
+    pub fn clear(&mut self) {
+        self.frames_since_launch = 0;
+    }
+
+    pub fn advance(&mut self) {
+        self.frames_since_launch = self.frames_since_launch.saturating_add(1);
+    }
+
+    pub fn can_stack(&self, minimum_frames: u32) -> bool {
+        self.frames_since_launch >= minimum_frames
+    }
+}
+
+fn stack_knockback_component(previous: FGi32, new: FGi32) -> FGi32 {
+    if previous.is_zero() {
+        return new;
+    }
+    if new.is_zero() {
+        return previous;
+    }
+
+    if previous.signum() != new.signum() {
+        previous + new
+    } else if previous.abs() > new.abs() {
+        previous
+    } else {
+        new
+    }
+}
+
+/// Applies Melee's knockback-stacking rule independently to both axes.
+pub fn stack_knockback(previous: FGVec2, new: FGVec2) -> FGVec2 {
+    FGVec2::new(
+        stack_knockback_component(previous.x, new.x),
+        stack_knockback_component(previous.y, new.y),
+    )
+}
+
+pub fn decay_knockback(
+    velocity: &mut FighterKnockbackVelocity,
+    state: &mut FighterKnockbackState,
+    decay_per_frame: FGi32,
+) {
+    let speed = velocity.length();
+    let next_speed = speed.saturating_sub(decay_per_frame).max(FGi32::ZERO);
+    velocity.0 = velocity.normalize_or_zero() * next_speed;
+
+    if next_speed.is_zero() {
+        state.clear();
+    } else {
+        state.advance();
+    }
+}
+
 #[derive(Debug, Default, Clone, Copy, Serialize, Deserialize, Component, Hash, PartialEq, Eq, PartialOrd, Ord)]
 pub struct FighterDamage(FGi32);
 
@@ -73,6 +142,53 @@ pub struct FighterLastAttackDebug {
     pub trajectory_points: Vec<Vec3>,
 }
 
+#[cfg(test)]
+mod knockback_stacking_tests {
+    use super::*;
+
+    #[test]
+    fn same_direction_keeps_the_stronger_component() {
+        assert_eq!(
+            stack_knockback(FGVec2::lit("3", "8"), FGVec2::lit("5", "4")),
+            FGVec2::lit("5", "8")
+        );
+    }
+
+    #[test]
+    fn opposing_components_add_independently() {
+        assert_eq!(
+            stack_knockback(FGVec2::lit("3", "8"), FGVec2::lit("-5", "-3")),
+            FGVec2::lit("-2", "5")
+        );
+    }
+
+    #[test]
+    fn opposing_components_can_cancel() {
+        assert_eq!(
+            stack_knockback(FGVec2::lit("3", "-4"), FGVec2::lit("-3", "4")),
+            FGVec2::ZERO
+        );
+    }
+
+    #[test]
+    fn zero_components_preserve_the_nonzero_value() {
+        assert_eq!(
+            stack_knockback(FGVec2::lit("0", "2"), FGVec2::lit("-3", "0")),
+            FGVec2::lit("-3", "2")
+        );
+    }
+
+    #[test]
+    fn stacking_threshold_is_inclusive() {
+        let mut state = FighterKnockbackState {
+            frames_since_launch: 9,
+        };
+        assert!(!state.can_stack(10));
+        state.advance();
+        assert!(state.can_stack(10));
+    }
+}
+
 #[derive(Debug, Default, Clone, Deref, DerefMut, Hash, PartialEq, PartialOrd)]
 pub struct HitStop(u32);
 
@@ -231,8 +347,8 @@ impl AttackKind {
             AttackKind::Jab => AnimKind::AttackJab1,
             AttackKind::UpTilt => AnimKind::AttackUpTilt,
             AttackKind::ForwardAir => AnimKind::AttackForwardAir,
+            AttackKind::DownAir => AnimKind::AttackDownAir,
             AttackKind::BackAir => AnimKind::AttackUpTilt,
-            AttackKind::DownAir => AnimKind::AttackUpTilt,
             AttackKind::UpAir => AnimKind::AttackUpTilt,
             AttackKind::DownTilt => AnimKind::AttackDownTilt,
             AttackKind::ForwardTilt => AnimKind::AttackForwardTilt,

src/fighter/baked_animation/asset_baking.rs

@@ -27,6 +27,7 @@ struct FighterBakeSource {
     model_bytes: Vec<u8>,
     buffers: Vec<Vec<u8>>,
     animations: HashMap<AnimKind, String>,
+    root_motion_bone: String,
 }
 #[derive(Default, TypePath)]
 struct FighterBakeSourceLoader;
@@ -82,6 +83,7 @@ impl AssetLoader for FighterBakeSourceLoader {
             model_bytes,
             buffers,
             animations: manifest.animations,
+            root_motion_bone: manifest.root_motion_bone,
         })
     }
     fn extensions(&self) -> &[&str] {
@@ -123,7 +125,12 @@ impl AssetTransformer for FighterBakeTransformer {
         source: TransformedAsset<Self::AssetInput>,
         _: &'a Self::Settings,
     ) -> Result<TransformedAsset<Self::AssetOutput>, Self::Error> {
-        let baked = bake_gltf(&source.model_bytes, &source.buffers, &source.animations)?;
+        let baked = bake_gltf(
+            &source.model_bytes,
+            &source.buffers,
+            &source.animations,
+            &source.root_motion_bone,
+        )?;
         Ok(source.replace_asset(baked))
     }
 }
@@ -201,6 +208,7 @@ fn bake_gltf(
     bytes: &[u8],
     buffer_bytes: &[Vec<u8>],
     animations: &HashMap<AnimKind, String>,
+    root_motion_bone: &str,
 ) -> io::Result<BakedFighterAnimations> {
     let gltf = gltf::Gltf::from_slice(bytes)
         .map_err(|error| io::Error::new(io::ErrorKind::InvalidData, error))?;
@@ -228,13 +236,14 @@ fn bake_gltf(
             "glTF buffer data is incomplete",
         ));
     }
-    bake_gltf_document(gltf.document, buffers, animations)
+    bake_gltf_document(gltf.document, buffers, animations, root_motion_bone)
 }
 
 pub(super) fn bake_gltf_document(
     document: gltf::Document,
     buffers: Vec<gltf::buffer::Data>,
     animations: &HashMap<AnimKind, String>,
+    root_motion_bone: &str,
 ) -> io::Result<BakedFighterAnimations> {
     let nodes: Vec<_> = document.nodes().collect();
     if nodes.is_empty() {
@@ -260,6 +269,15 @@ pub(super) fn bake_gltf_document(
             })
         })
         .collect::<io::Result<Vec<_>>>()?;
+    let root_bone_index = names
+        .iter()
+        .position(|name| name == root_motion_bone)
+        .ok_or_else(|| {
+            io::Error::new(
+                io::ErrorKind::InvalidData,
+                format!("fighter model has no root-motion bone named {root_motion_bone}"),
+            )
+        })?;
     let mut pending = HashMap::<&str, Vec<AnimKind>>::new();
     for (kind, name) in animations {
         pending.entry(name).or_default().push(*kind);
@@ -286,17 +304,28 @@ pub(super) fn bake_gltf_document(
             .fold(0.0_f32, f32::max);
         let frame_count = baked_frame_count(duration, BAKED_ANIMATION_FPS);
         let mut frames = Vec::with_capacity(frame_count);
+        let mut root_positions = Vec::with_capacity(frame_count);
         for frame in 0..frame_count {
             let time = (frame as f32 / BAKED_ANIMATION_FPS as f32).min(duration);
-            frames.push(
+            let local = nodes
-                nodes
+                .iter()
-                    .iter()
+                .map(|node| local_transform(node.clone(), &channels, time))
-                    .map(|node| local_transform(node.clone(), &channels, time))
+                .collect::<io::Result<Vec<_>>>()?;
-                    .collect::<io::Result<Vec<_>>>()?,
+            let mut model = vec![None; local.len()];
-            );
+            let root = super::runtime::resolve_model_transform(
+                root_bone_index,
+                &parents,
+                &local,
+                &mut model,
+            )?;
+            root_positions.push(root.get_translation());
+            frames.push(local);
         }
         let index = clips.len();
-        clips.push(BakedAnimationClip { frames });
+        clips.push(BakedAnimationClip {
+            frames,
+            root_positions,
+        });
         for kind in kinds {
             clip_indices.insert(kind, index);
         }
@@ -322,6 +351,7 @@ pub(super) fn bake_gltf_document(
         frame_rate: BAKED_ANIMATION_FPS,
         bone_names: names,
         parents,
+        root_bone_index,
         clips,
         clip_indices,
     })

src/fighter/baked_animation/mod.rs

@@ -36,7 +36,13 @@ mod tests {
         ))
         .unwrap();
         let (document, buffers) = test_gltf(&manifest.animations);
-        let baked = bake_gltf_document(document, buffers, &manifest.animations).unwrap();
+        let baked = bake_gltf_document(
+            document,
+            buffers,
+            &manifest.animations,
+            &manifest.root_motion_bone,
+        )
+        .unwrap();
 
         assert_eq!(baked.frame_rate, BAKED_ANIMATION_FPS);
         assert_eq!(baked.frame_count(AnimKind::Wait), Some(121));
@@ -51,6 +57,15 @@ mod tests {
             baked.bone_names.len()
         );
         assert_eq!(baked.parents.len(), baked.bone_names.len());
+        assert_eq!(baked.root_bone_index, 0);
+        assert_eq!(
+            baked.initial_root_position(AnimKind::Wait, FGi32::lit("2")),
+            Some(FGVec3::ZERO)
+        );
+        assert_eq!(
+            baked.root_motion_cycle_delta(AnimKind::Wait, FGi32::lit("2")),
+            Some(FGVec3::lit("2", "0", "0"))
+        );
     }
 
     /// Builds the smallest glTF document that still exercises the complete
@@ -162,8 +177,14 @@ mod tests {
             frame_rate: BAKED_ANIMATION_FPS,
             bone_names: vec!["root".into()],
             parents: vec![None],
+            root_bone_index: 0,
             clips: vec![BakedAnimationClip {
                 frames: vec![vec![first], vec![second], vec![terminal]],
+                root_positions: vec![
+                    FGVec3::ZERO,
+                    FGVec3::lit("2", "0", "0"),
+                    FGVec3::lit("4", "0", "0"),
+                ],
             }],
             clip_indices: HashMap::from([(AnimKind::Wait, 0)]),
         };
@@ -339,7 +360,8 @@ mod tests {
 
         matrices.set_pose_with_frame(
             frame,
-            "root",
+            Some(0),
+            Some(FGVec3::lit("2", "0", "0")),
             FGVec3::ZERO,
             None,
             AnimKind::Wait,
@@ -349,10 +371,15 @@ mod tests {
             FGi32::lit("2"),
         );
         assert_eq!(matrices.root_motion_delta(), FGVec3::ZERO);
+        assert_eq!(
+            matrices.root_motion_position(),
+            Some(FGVec3::lit("2", "0", "0"))
+        );
 
         matrices.set_pose_with_frame(
             crate::fighter::animation::FighterAnimationFrame { frame: 1, ..frame },
-            "root",
+            Some(0),
+            Some(FGVec3::lit("6", "0", "0")),
             FGVec3::ZERO,
             None,
             AnimKind::Wait,
@@ -377,7 +404,8 @@ mod tests {
 
         matrices.set_pose_with_frame(
             frame,
-            "root",
+            Some(0),
+            Some(FGVec3::lit("3", "4", "5")),
             FGVec3::ZERO,
             None,
             AnimKind::Wait,
@@ -397,7 +425,69 @@ mod tests {
     }
 
     #[test]
-    fn repeating_root_motion_preserves_cycle_displacement_at_wrap() {
+    fn every_animation_extracts_root_translation_and_retains_its_position() {
+        let names = ["root".into(), "hand".into()];
+        let parents = [None, Some(0)];
+        let mut root = FixedMat4::IDENTITY;
+        root.translate(FGVec3::lit("3", "4", "5"));
+        let mut hand = FixedMat4::IDENTITY;
+        hand.translate(FGVec3::lit("1", "2", "0"));
+        let mut matrices = FighterBoneMatrices::default();
+        let frame = crate::fighter::animation::FighterAnimationFrame::new(
+            AnimKind::LedgeWait,
+            true,
+        );
+
+        matrices.set_pose_with_frame(
+            frame,
+            Some(0),
+            Some(FGVec3::lit("3", "4", "5")),
+            FGVec3::ZERO,
+            None,
+            AnimKind::LedgeWait,
+            &names,
+            &parents,
+            &[root, hand],
+            FGi32::ONE,
+        );
+
+        assert_eq!(matrices.root_motion_delta(), FGVec3::ZERO);
+        assert_eq!(
+            matrices.root_motion_position(),
+            Some(FGVec3::lit("3", "4", "5"))
+        );
+        assert_eq!(matrices.local(0).unwrap().get_translation(), FGVec3::ZERO);
+        assert_eq!(
+            matrices.get_current("root").unwrap().get_translation(),
+            FGVec3::ZERO
+        );
+        assert_eq!(
+            matrices.get_current("hand").unwrap().get_translation(),
+            FGVec3::lit("1", "2", "0")
+        );
+
+        root.translate(FGVec3::lit("6", "4", "5"));
+        matrices.set_pose_with_frame(
+            crate::fighter::animation::FighterAnimationFrame { frame: 1, ..frame },
+            Some(0),
+            Some(FGVec3::lit("6", "4", "5")),
+            FGVec3::ZERO,
+            None,
+            AnimKind::LedgeWait,
+            &names,
+            &parents,
+            &[root, hand],
+            FGi32::ONE,
+        );
+        assert_eq!(matrices.root_motion_delta(), FGVec3::lit("3", "0", "0"));
+        assert_eq!(
+            matrices.get_current("root").unwrap().get_translation(),
+            FGVec3::ZERO
+        );
+    }
+
+    #[test]
+    fn repeating_root_motion_preserves_cycle_displacement_at_every_wrap() {
         let names = ["root".into()];
         let parents = [None];
         let pose = |x| FixedMat4::IDENTITY.with_translation(FGVec3::lit(x, "0", "0"));
@@ -408,10 +498,17 @@ mod tests {
             repeat: true,
         };
 
-        for (frame_number, x) in [(0, "0"), (1, "1")] {
+        for (frame_number, x, expected_delta) in [
+            (0, "0", FGVec3::ZERO),
+            (1, "1", FGVec3::lit("1", "0", "0")),
+            (2, "0", FGVec3::lit("1", "0", "0")),
+            (3, "1", FGVec3::lit("1", "0", "0")),
+            (4, "0", FGVec3::lit("1", "0", "0")),
+        ] {
             matrices.set_pose_with_frame(
                 frame(frame_number),
-                "root",
+                Some(0),
+                Some(FGVec3::lit(x, "0", "0")),
                 FGVec3::lit("2", "0", "0"),
                 Some(2),
                 AnimKind::Wait,
@@ -420,19 +517,8 @@ mod tests {
                 &[pose(x)],
                 FGi32::ONE,
             );
+            assert_eq!(matrices.root_motion_delta(), expected_delta);
         }
-        matrices.set_pose_with_frame(
-            frame(2),
-            "root",
-            FGVec3::lit("2", "0", "0"),
-            Some(2),
-            AnimKind::Wait,
-            &names,
-            &parents,
-            &[pose("0")],
-            FGi32::ONE,
-        );
-        assert_eq!(matrices.root_motion_delta(), FGVec3::lit("1", "0", "0"));
     }
 
     #[test]

src/fighter/baked_animation/runtime.rs

@@ -21,6 +21,9 @@ use crate::{
 #[derive(Clone, Debug, Serialize, Deserialize)]
 pub struct BakedAnimationClip {
     pub frames: Vec<Vec<FixedMat4>>,
+    /// Unscaled model-space position of the configured root-motion bone at
+    /// each baked frame.
+    pub root_positions: Vec<FGVec3>,
 }
 
 #[derive(Asset, bevy::reflect::TypePath, Clone, Debug, Serialize, Deserialize)]
@@ -29,11 +32,22 @@ pub struct BakedFighterAnimations {
     pub frame_rate: u32,
     pub bone_names: Vec<String>,
     pub parents: Vec<Option<usize>>,
+    pub(super) root_bone_index: usize,
     pub(super) clips: Vec<BakedAnimationClip>,
     pub(super) clip_indices: HashMap<AnimKind, usize>,
 }
 
 impl BakedFighterAnimations {
+    fn sample_index(&self, frame: &FighterAnimationFrame) -> Option<usize> {
+        let frames = &self.clip(frame.kind)?.frames;
+        let frame_index = if frame.repeat {
+            let loop_frame_count = frames.len().saturating_sub(1).max(1) as u32;
+            frame.frame % loop_frame_count
+        } else {
+            frame.frame
+        };
+        Some((frame_index as usize).min(frames.len().saturating_sub(1)))
+    }
     pub fn contains_bone(&self, bone: &str) -> bool {
         self.bone_names.iter().any(|name| name == bone)
     }
@@ -42,17 +56,20 @@ impl BakedFighterAnimations {
         self.bone_names.iter().all(|name| names.insert(name))
     }
     pub fn sample_pose(&self, frame: &FighterAnimationFrame) -> Option<&[FixedMat4]> {
-        let frames = &self.clip(frame.kind)?.frames;
+        let clip = self.clip(frame.kind)?;
-        let frame_index = if frame.repeat {
+        clip.frames.get(self.sample_index(frame)?).map(Vec::as_slice)
-            let loop_frame_count = frames.len().saturating_sub(1).max(1) as u32;
+    }
-            frame.frame % loop_frame_count
+    pub fn sample_root_position(
-        } else {
+        &self,
-            frame.frame
+        frame: &FighterAnimationFrame,
-        };
+        model_scale: FGi32,
-        frames
+    ) -> Option<FGVec3> {
-            .get(frame_index as usize)
+        let clip = self.clip(frame.kind)?;
-            .or_else(|| frames.last())
+        let position = *clip.root_positions.get(self.sample_index(frame)?)?;
-            .map(Vec::as_slice)
+        Some(position * model_scale)
+    }
+    pub fn initial_root_position(&self, kind: AnimKind, model_scale: FGi32) -> Option<FGVec3> {
+        self.sample_root_position(&FighterAnimationFrame::new(kind, false), model_scale)
     }
     pub fn frame_count(&self, kind: AnimKind) -> Option<u32> {
         self.clip(kind).map(|clip| clip.frames.len() as u32)
@@ -60,27 +77,10 @@ impl BakedFighterAnimations {
     pub fn root_motion_cycle_delta(
         &self,
         kind: AnimKind,
-        bone: &str,
         model_scale: FGi32,
     ) -> Option<FGVec3> {
-        let last = self.frame_count(kind)?.saturating_sub(1);
+        let clip = self.clip(kind)?;
-        let first = FighterAnimationFrame {
+        Some((*clip.root_positions.last()? - *clip.root_positions.first()?) * model_scale)
-            kind,
-            frame: 0,
-            repeat: false,
-        };
-        let last = FighterAnimationFrame {
-            kind,
-            frame: last,
-            repeat: false,
-        };
-        Some(
-            self.sample_bone_model_transform(&last, bone, model_scale)?
-                .get_translation()
-                - self
-                    .sample_bone_model_transform(&first, bone, model_scale)?
-                    .get_translation(),
-        )
     }
     /// Samples one bone in model space without depending on the runtime's
     /// previous-frame buffers. Tooling uses this when the user scrubs between
@@ -110,6 +110,9 @@ impl BakedFighterAnimations {
             .get(&kind)
             .and_then(|index| self.clips.get(*index))
     }
+    pub fn get_animation_duration(&self, kind: AnimKind) -> Option<usize> {
+        self.clip(kind).map(|clip| clip.frames.len())
+    }
 }
 
 #[derive(Component, Clone, Debug, Default, Hash)]
@@ -124,13 +127,12 @@ pub struct FighterBoneMatrices {
     model_matrices: Vec<Option<FixedMat4>>,
     presentation_kind: Option<AnimKind>,
     previous_animation_frame: Option<FighterAnimationFrame>,
+    root_motion_position: Option<FGVec3>,
     /// The raw, scaled model-space root translation used as the baseline for
     /// root-motion extraction.  This is kept separately because the published
     /// pose has the root translation removed.
     previous_root_motion_translation: Option<FGVec3>,
     root_motion_delta: crate::math::vec3::FGVec3,
-    cached_root_motion_kind: Option<AnimKind>,
-    cached_root_motion_cycle_delta: FGVec3,
 }
 
 #[derive(Component, Clone, Debug, Default)]
@@ -149,7 +151,8 @@ impl FighterBoneMatrices {
         };
         self.set_pose_with_frame(
             *frame,
-            "root",
+            Some(baked.root_bone_index),
+            baked.sample_root_position(frame, model_scale),
             FGVec3::ZERO,
             None,
             frame.kind,
@@ -203,6 +206,11 @@ impl FighterBoneMatrices {
     pub fn root_motion_delta(&self) -> FGVec3 {
         self.root_motion_delta
     }
+    /// Current raw, scaled model-space position of the configured root-motion
+    /// bone. The published skeleton has this translation removed.
+    pub fn root_motion_position(&self) -> Option<FGVec3> {
+        self.root_motion_position
+    }
     pub fn iter(&self) -> impl Iterator<Item = (&str, FixedMat4)> {
         self.bone_names
             .iter()
@@ -236,7 +244,8 @@ impl FighterBoneMatrices {
     ) {
         self.set_pose_with_frame(
             FighterAnimationFrame::new(kind, false),
-            "",
+            None,
+            None,
             FGVec3::ZERO,
             None,
             kind,
@@ -249,7 +258,8 @@ impl FighterBoneMatrices {
     pub(super) fn set_pose_with_frame(
         &mut self,
         animation_frame: FighterAnimationFrame,
-        root_motion_bone: &str,
+        root_bone_index: Option<usize>,
+        root_motion_position: Option<FGVec3>,
         root_motion_cycle_delta: FGVec3,
         root_motion_loop_frame_count: Option<u32>,
         kind: AnimKind,
@@ -260,7 +270,8 @@ impl FighterBoneMatrices {
     ) {
         self.sample_pose(
             animation_frame,
-            root_motion_bone,
+            root_bone_index,
+            root_motion_position,
             root_motion_cycle_delta,
             root_motion_loop_frame_count,
             kind,
@@ -282,7 +293,8 @@ impl FighterBoneMatrices {
     ) {
         self.resample_pose_with_frame(
             FighterAnimationFrame::new(kind, false),
-            "",
+            None,
+            None,
             FGVec3::ZERO,
             None,
             kind,
@@ -295,7 +307,8 @@ impl FighterBoneMatrices {
     pub(super) fn resample_pose_with_frame(
         &mut self,
         animation_frame: FighterAnimationFrame,
-        root_motion_bone: &str,
+        root_bone_index: Option<usize>,
+        root_motion_position: Option<FGVec3>,
         _root_motion_cycle_delta: FGVec3,
         _root_motion_loop_frame_count: Option<u32>,
         kind: AnimKind,
@@ -306,7 +319,8 @@ impl FighterBoneMatrices {
     ) {
         self.sample_pose(
             animation_frame,
-            root_motion_bone,
+            root_bone_index,
+            root_motion_position,
             FGVec3::ZERO,
             None,
             kind,
@@ -320,7 +334,8 @@ impl FighterBoneMatrices {
     fn sample_pose(
         &mut self,
         animation_frame: FighterAnimationFrame,
-        root_motion_bone: &str,
+        root_index: Option<usize>,
+        raw_root_motion_translation: Option<FGVec3>,
         root_motion_cycle_delta: FGVec3,
         root_motion_loop_frame_count: Option<u32>,
         kind: AnimKind,
@@ -360,16 +375,6 @@ impl FighterBoneMatrices {
         self.local_matrices.clear();
         self.local_matrices.extend_from_slice(local);
 
-        let root_index = if root_motion_bone.is_empty() {
-            None
-        } else {
-            Some(
-                self.bone_names
-                    .iter()
-                    .position(|name| name == root_motion_bone)
-                    .expect("configured root motion bone should exist"),
-            )
-        };
         let model_scale = FixedMat4 {
             cols: [
                 [model_scale, FGi32::ZERO, FGi32::ZERO, FGi32::ZERO],
@@ -378,21 +383,8 @@ impl FighterBoneMatrices {
                 [FGi32::ZERO, FGi32::ZERO, FGi32::ZERO, FGi32::ONE],
             ],
         };
-        // Root motion only needs the configured bone's model transform. Resolve
+        // Gameplay always owns root displacement. Keep rotation and scale in
-        // that ancestry first, then do the normal full-pose pass once below.
+        // the pose while removing the configured root bone's translation.
-        // Previously the complete hierarchy was resolved once before removing
-        // root translation and once afterwards.
-        let raw_root_motion_translation = root_index.map(|root_index| {
-            self.model_matrices.resize(local.len(), None);
-            self.model_matrices.fill(None);
-            let root = resolve_model_transform(root_index, parents, local, &mut self.model_matrices)
-                .expect("baked bone hierarchy should be valid");
-            model_scale.mul(root).get_translation()
-        });
-
-        // Gameplay owns the root's displacement.  Keep rotation and scale in
-        // the animation, but remove its translation before publishing the pose
-        // used by visuals and gameplay volumes.
         if let Some(root_index) = root_index {
             self.local_matrices[root_index].translate(FGVec3::ZERO);
         }
@@ -419,9 +411,12 @@ impl FighterBoneMatrices {
             let mut delta = current - previous;
             if animation_frame.repeat
                 && self.previous_animation_frame.is_some_and(|previous| {
-                    previous.frame.saturating_add(1) == animation_frame.frame
+                    previous.kind == animation_frame.kind
+                        && previous.frame.saturating_add(1) == animation_frame.frame
+                })
+                && root_motion_loop_frame_count.is_some_and(|loop_frame_count| {
+                    loop_frame_count > 0 && animation_frame.frame % loop_frame_count == 0
                 })
-                && root_motion_loop_frame_count == Some(animation_frame.frame)
             {
                 delta = delta + root_motion_cycle_delta;
             }
@@ -429,6 +424,7 @@ impl FighterBoneMatrices {
         } else {
             FGVec3::ZERO
         };
+        self.root_motion_position = raw_root_motion_translation;
         self.previous_root_motion_translation = raw_root_motion_translation;
         if advance_history {
             self.previous_animation_frame = Some(animation_frame);
@@ -519,23 +515,18 @@ fn sample_fighter_bone_matrices(
     let manifest = manifests
         .get(&fighter.manifest)
         .expect("fighter manifest should be loaded before the match starts");
-    let root_motion_cycle_delta = if matrices.cached_root_motion_kind == Some(frame.kind) {
+    let root_motion_position = baked.sample_root_position(frame, manifest.model_scale);
-        matrices.cached_root_motion_cycle_delta
+    let root_motion_cycle_delta = baked
-    } else {
+        .root_motion_cycle_delta(frame.kind, manifest.model_scale)
-        let delta = baked
+        .unwrap_or(FGVec3::ZERO);
-            .root_motion_cycle_delta(frame.kind, &manifest.root_motion_bone, manifest.model_scale)
-            .unwrap_or(FGVec3::ZERO);
-        matrices.cached_root_motion_kind = Some(frame.kind);
-        matrices.cached_root_motion_cycle_delta = delta;
-        delta
-    };
     let root_motion_loop_frame_count = baked
         .frame_count(frame.kind)
         .map(|count| count.saturating_sub(1).max(1));
     if advance_history {
         matrices.set_pose_with_frame(
             *frame,
-            &manifest.root_motion_bone,
+            Some(baked.root_bone_index),
+            root_motion_position,
             root_motion_cycle_delta,
             root_motion_loop_frame_count,
             frame.kind,
@@ -547,7 +538,8 @@ fn sample_fighter_bone_matrices(
     } else {
         matrices.resample_pose_with_frame(
             *frame,
-            &manifest.root_motion_bone,
+            Some(baked.root_bone_index),
+            root_motion_position,
             FGVec3::ZERO,
             None,
             frame.kind,
@@ -568,7 +560,7 @@ fn sample_fighter_bone_matrices(
     }
 }
 
-fn resolve_model_transform(
+pub(super) fn resolve_model_transform(
     index: usize,
     parents: &[Option<usize>],
     local: &[FixedMat4],

src/fighter/collision.rs

@@ -1,10 +1,17 @@
 //! Resolving an integrated fighter position against the stage.
 
-use crate::fighter::ecb::FighterPreviousECB;
+use crate::fighter::ecb::{self as ecb_module, FighterDesiredECB};
-use crate::fighter::{FighterECB, FighterPreviousTranslation, FighterTranslation};
+use crate::fighter::{FighterPreviousTranslation, FighterTranslation};
+use crate::fighter::FighterVelocity;
+#[cfg(test)]
+use crate::fighter::{FighterECB, ecb::FighterPreviousECB};
+use crate::math::int::FGi32;
+use crate::math::rect::FGRect;
 use crate::math::segment::FGSegment2d;
 use crate::math::vec::FGVec2;
-use crate::stage::line::{StageCollision, StageLineID, StagePolyType};
+use crate::stage::line::{
+    StageCollision, StageLineID, StagePolyLineSegmentType, StagePolyType, StageVertexID,
+};
 /*
 pub fn collide_fighter_with_scene(
     fighters: Query<(&FighterECB, &mut FighterVelocity, &mut FighterTranslation)>,
@@ -35,54 +42,411 @@ pub fn collide_fighter_with_scene(
 pub struct AirCollisionWithStageResult {
     pub line_id: StageLineID,
     pub hit_position: FGVec2,
+    /// Fighter origin at the collision substep. The ECB remains local to this
+    /// origin; callers must not rebase the ECB by the frame-sized movement.
+    pub resolved_translation: FGVec2,
     pub hit_normal: FGVec2,
 }
 
-pub fn air_collide_with_stage(
+#[derive(Clone, Copy, Debug, Default)]
+pub struct AirCollisionOptions {
+    /// Allow downward input to disable collision with pass-through platforms.
+    pub can_pass_through_soft_platforms: bool,
+    /// Treat an upward crossing of a pass-through platform by the ECB bottom as a landing.
+    pub land_on_soft_platforms_from_below: bool,
+}
+
+#[cfg(test)]
+fn air_collide_with_stage(
     prev_translation: &FighterPreviousTranslation,
     translation: &FighterTranslation,
     prev_ecb: &FighterPreviousECB,
     ecb: &FighterECB,
     stage_collision: &StageCollision,
     ignored_polys: &[usize],
-    can_ignore_soft_platforms: bool,
+    options: AirCollisionOptions,
 ) -> Option<AirCollisionWithStageResult> {
-    let ray_segment = FGSegment2d::new(
+    let mut translation = *translation;
-        prev_translation.0 + prev_ecb.get_bottom_point(),
+    let mut velocity = FighterVelocity::default();
-        translation.0 + ecb.get_bottom_point(),
+    air_collide_with_stage_substepped(
-    );
+        prev_translation,
+        &mut translation,
+        &mut velocity,
+        &mut ecb_module::FighterECB {
+            top: prev_ecb.top,
+            bottom: prev_ecb.bottom,
+            left: prev_ecb.left,
+            right: prev_ecb.right,
+        },
+        &FighterDesiredECB::from(*ecb),
+        stage_collision,
+        ignored_polys,
+        options,
+    )
+}
+
+/// Sweeps movement and ECB shape changes together.
+pub(crate) fn collision_step_count(max_change: FGi32) -> u32 {
+    let six = FGi32::lit("6.0");
+    if max_change <= six {
+        return 1;
+    }
+
+    let mut quotient = 0;
+    let mut remainder = max_change;
+    while remainder >= six {
+        quotient += 1;
+        remainder -= six;
+    }
+    quotient + 1
+}
+
+pub fn air_collide_with_stage_substepped(
+    prev_translation: &FighterPreviousTranslation,
+    translation: &mut FighterTranslation,
+    velocity: &mut FighterVelocity,
+    ecb: &mut crate::fighter::FighterECB,
+    desired: &FighterDesiredECB,
+    stage_collision: &StageCollision,
+    ignored_polys: &[usize],
+    options: AirCollisionOptions,
+) -> Option<AirCollisionWithStageResult> {
+    let requested_translation = translation.0;
+    let movement = requested_translation - prev_translation.0;
+    let mut largest_change = movement.x.abs().max(movement.y.abs());
+    largest_change = largest_change.max(ecb_module::ecb_max_delta(ecb, desired));
+    let steps = collision_step_count(largest_change);
+
+    let step_count = FGi32::from_num(steps);
+    let movement_per_step = movement / step_count;
+    let mut current_position = prev_translation.0;
+    let mut current_ecb = *ecb;
+    let mut collision_offset = FGVec2::ZERO;
+
+    for step in 0..steps {
+        let previous_position = current_position;
+        let previous_ecb = current_ecb;
+        let remaining_steps = FGi32::from_num(steps - step);
+        ecb_module::interpolate_ecb(&mut current_ecb, *desired, FGi32::ONE / remaining_steps);
+        current_position = if step + 1 == steps {
+            // Fixed-point division may truncate. Always make the final
+            // substep land exactly on the requested frame endpoint.
+            requested_translation + collision_offset
+        } else {
+            prev_translation.0
+                + movement_per_step * FGi32::from_num(step + 1)
+                + collision_offset
+        };
+
+        let lower_edges = [
+            (
+                previous_ecb.bottom,
+                previous_ecb.left,
+                current_ecb.bottom,
+                current_ecb.left,
+            ),
+            (
+                previous_ecb.bottom,
+                previous_ecb.right,
+                current_ecb.bottom,
+                current_ecb.right,
+            ),
+        ];
+        if let Some(result) = sweep_edges(
+            stage_collision,
+            previous_position,
+            current_position,
+            &lower_edges,
+            StagePolyLineSegmentType::Floor,
+            ignored_polys,
+            options.can_pass_through_soft_platforms,
+        ) {
+            *ecb = current_ecb;
+            translation.0 = current_position + result.correction;
+            velocity.0 -= velocity.0.project_onto_normalized(result.hit_normal);
+            let bottom_contact = translation.0 + current_ecb.bottom;
+            return Some(AirCollisionWithStageResult {
+                line_id: result.line_id,
+                hit_position: bottom_contact,
+                resolved_translation: translation.0,
+                hit_normal: result.hit_normal,
+            });
+        }
+
+        let upper_edges = [
+            (
+                previous_ecb.top,
+                previous_ecb.left,
+                current_ecb.top,
+                current_ecb.left,
+            ),
+            (
+                previous_ecb.top,
+                previous_ecb.right,
+                current_ecb.top,
+                current_ecb.right,
+            ),
+        ];
+        if let Some(contact) = sweep_edges(
+            stage_collision,
+            previous_position,
+            current_position,
+            &upper_edges,
+            StagePolyLineSegmentType::Ceiling,
+            ignored_polys,
+            true,
+        ) {
+            current_position += contact.correction;
+            collision_offset += contact.correction;
+            velocity.0 -= velocity.0.project_onto_normalized(contact.hit_normal);
+        }
+
+        if options.land_on_soft_platforms_from_below
+            && let Some(result) = sweep_bottom_point_through_platforms(
+                stage_collision,
+                previous_position + previous_ecb.bottom,
+                current_position + current_ecb.bottom,
+                ignored_polys,
+            )
+        {
+            *ecb = current_ecb;
+            translation.0 = current_position + result.correction;
+            velocity.0 -= velocity.0.project_onto_normalized(result.hit_normal);
+            let bottom_contact = translation.0 + current_ecb.bottom;
+            return Some(AirCollisionWithStageResult {
+                line_id: result.line_id,
+                hit_position: bottom_contact,
+                resolved_translation: translation.0,
+                hit_normal: result.hit_normal,
+            });
+        }
+
+        let side_edges = [
+            (
+                previous_ecb.bottom,
+                previous_ecb.right,
+                current_ecb.bottom,
+                current_ecb.right,
+            ),
+            (
+                previous_ecb.right,
+                previous_ecb.top,
+                current_ecb.right,
+                current_ecb.top,
+            ),
+            (
+                previous_ecb.top,
+                previous_ecb.left,
+                current_ecb.top,
+                current_ecb.left,
+            ),
+            (
+                previous_ecb.left,
+                previous_ecb.bottom,
+                current_ecb.left,
+                current_ecb.bottom,
+            ),
+        ];
+        if let Some(contact) = sweep_edges(
+            stage_collision,
+            previous_position,
+            current_position,
+            &side_edges,
+            StagePolyLineSegmentType::Wall,
+            ignored_polys,
+            true,
+        ) {
+            current_position += contact.correction;
+            collision_offset += contact.correction;
+            velocity.0 -= velocity.0.project_onto_normalized(contact.hit_normal);
+        }
+    }
+
+    *ecb = current_ecb;
+    translation.0 = current_position;
+    None
+}
+
+struct PointSweepResult {
+    line_id: StageLineID,
+    hit_normal: FGVec2,
+    correction: FGVec2,
+}
+
+fn sweep_bottom_point_through_platforms(
+    stage_collision: &StageCollision,
+    previous_bottom: FGVec2,
+    current_bottom: FGVec2,
+    ignored_polys: &[usize],
+) -> Option<PointSweepResult> {
+    let bottom_sweep = FGSegment2d::new(previous_bottom, current_bottom);
 
     stage_collision
         .stage_polys
         .iter()
         .enumerate()
         .filter(|(poly_idx, poly)| {
-            !ignored_polys.contains(poly_idx)
+            !ignored_polys.contains(poly_idx) && matches!(poly.poly_type, StagePolyType::Platform)
-                && !(can_ignore_soft_platforms && matches!(poly.poly_type, StagePolyType::Platform))
         })
-        .filter_map(|(poly_idx, poly)| {
+        .flat_map(|(poly_idx, poly)| {
-            poly.intersect_ray(ray_segment).map(|intersect_result| {
+            poly.segments
-                (
+                .iter()
-                    AirCollisionWithStageResult {
+                .enumerate()
-                        line_id: {
+                .filter(|(_, segment)| {
-                            StageLineID {
+                    matches!(segment.segment_type, StagePolyLineSegmentType::Floor)
+                })
+                .filter_map(move |(segment_idx, segment)| {
+                    let previous_distance = segment
+                        .normal
+                        .dot(previous_bottom - segment.segment.point1());
+                    let current_distance = segment
+                        .normal
+                        .dot(current_bottom - segment.segment.point1());
+                    if previous_distance >= crate::math::int::FGWide::ZERO
+                        || current_distance < crate::math::int::FGWide::ZERO
+                    {
+                        return None;
+                    }
+
+                    let hit_position = segment.segment.segment_intersection(&bottom_sweep)?;
+                    Some((
+                        PointSweepResult {
+                            line_id: StageLineID {
                                 polygon: poly_idx,
-                                segment: intersect_result.segment_idx,
+                                segment: segment_idx,
-                            }
+                            },
+                            hit_normal: segment.normal,
+                            correction: hit_position - current_bottom,
                         },
-                        hit_position: intersect_result.position,
+                        hit_position.distance_squared(previous_bottom),
-                        hit_normal: intersect_result.normal,
+                    ))
-                    },
+                })
-                    intersect_result
+        })
-                        .position
+        .min_by_key(|(_, distance)| *distance)
-                        .distance_squared(ray_segment.point2()),
+        .map(|(result, _)| result)
-                )
+}
-            })
+
+fn sweep_edges(
+    stage_collision: &StageCollision,
+    previous_position: FGVec2,
+    current_position: FGVec2,
+    edges: &[(FGVec2, FGVec2, FGVec2, FGVec2)],
+    segment_type: StagePolyLineSegmentType,
+    ignored_polys: &[usize],
+    ignore_platforms: bool,
+) -> Option<PointSweepResult> {
+    stage_collision
+        .stage_polys
+        .iter()
+        .enumerate()
+        .filter(|(poly_idx, poly)| {
+            !ignored_polys.contains(poly_idx)
+                && !(ignore_platforms && matches!(poly.poly_type, StagePolyType::Platform))
+        })
+        .flat_map(|(poly_idx, poly)| {
+            poly.segments
+                .iter()
+                .enumerate()
+                .filter(move |(_, segment)| segment.segment_type == segment_type)
+                .filter_map(move |(segment_idx, segment)| {
+                    edges
+                        .iter()
+                        .filter_map(|(previous_a, previous_b, current_a, current_b)| {
+                            let previous_a = previous_position + *previous_a;
+                            let previous_b = previous_position + *previous_b;
+                            let current_a = current_position + *current_a;
+                            let current_b = current_position + *current_b;
+                            let previous_min = segment
+                                .normal
+                                .dot(previous_a - segment.segment.point1())
+                                .min(segment.normal.dot(previous_b - segment.segment.point1()));
+                            let current_a_distance =
+                                segment.normal.dot(current_a - segment.segment.point1());
+                            let current_b_distance =
+                                segment.normal.dot(current_b - segment.segment.point1());
+                            let current_min = current_a_distance.min(current_b_distance);
+                            if previous_min < crate::math::int::FGWide::ZERO
+                                || current_min > crate::math::int::FGWide::ZERO
+                            {
+                                return None;
+                            }
+
+                            let boundary = [
+                                FGSegment2d::new(previous_a, previous_b),
+                                FGSegment2d::new(previous_a, current_a),
+                                FGSegment2d::new(previous_b, current_b),
+                                FGSegment2d::new(current_a, current_b),
+                            ];
+                            let quad = [previous_a, previous_b, current_b, current_a];
+                            let position = boundary
+                                .iter()
+                                .filter_map(|edge| segment.segment.segment_intersection(edge))
+                                .max_by_key(|position| position.distance_squared(current_a))
+                                .or_else(|| {
+                                    [segment.segment.point1(), segment.segment.point2()]
+                                        .into_iter()
+                                        .find(|point| point_in_convex_quad(*point, quad))
+                                })?;
+                            let penetration = FGi32::from_num(-current_min);
+                            Some((position, segment.normal * penetration))
+                        })
+                        .max_by_key(|(position, _)| {
+                            position.distance_squared(segment.segment.point1())
+                        })
+                        .map(|(position, correction)| {
+                            (
+                                PointSweepResult {
+                                    line_id: StageLineID {
+                                        polygon: poly_idx,
+                                        segment: segment_idx,
+                                    },
+                                    hit_normal: segment.normal,
+                                    correction,
+                                },
+                                position.distance_squared(segment.segment.point2()),
+                            )
+                        })
+                })
         })
         .max_by(|(_, a), (_, b)| a.cmp(b))
         .map(|(result, _)| result)
 }
 
+fn point_in_convex_quad(point: FGVec2, quad: [FGVec2; 4]) -> bool {
+    let mut has_positive = false;
+    let mut has_negative = false;
+    for (a, b) in quad.into_iter().zip(quad.into_iter().cycle().skip(1)).take(4) {
+        let edge = b - a;
+        let offset = point - a;
+        let cross = crate::math::int::FGWide::from_num(edge.x)
+            * crate::math::int::FGWide::from_num(offset.y)
+            - crate::math::int::FGWide::from_num(edge.y)
+                * crate::math::int::FGWide::from_num(offset.x);
+        has_positive |= cross > crate::math::int::FGWide::ZERO;
+        has_negative |= cross < crate::math::int::FGWide::ZERO;
+        if has_positive && has_negative {
+            return false;
+        }
+    }
+    true
+}
+
+#[derive(Clone)]
+pub struct AirCollisionWithLedgeResult {
+    pub ledge: StageVertexID,
+}
+
+pub fn air_collide_with_ledges(
+    ledge_box: &FGRect,
+    stage_collision: &StageCollision,
+) -> Option<AirCollisionWithLedgeResult> {
+    stage_collision
+        .intersect_ledges(ledge_box)
+        .map(|result| AirCollisionWithLedgeResult {
+            ledge: result.vertex_id,
+        })
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -111,10 +475,178 @@ mod tests {
         )
     }
 
+    fn single_segment(
+        start: FGVec2,
+        end: FGVec2,
+        segment_type: StagePolyLineSegmentType,
+    ) -> StagePoly {
+        let segment = FGSegment2d::new(start, end);
+        StagePoly {
+            poly_type: StagePolyType::Closed,
+            segments: vec![crate::stage::line::StagePolyLineSegment {
+                segment,
+                normal: segment.left_normal(),
+                segment_type,
+            }],
+        }
+    }
+
+    #[test]
+    fn melee_step_count_adds_one_step_after_each_six_unit_block() {
+        assert_eq!(collision_step_count(FGi32::lit("6")), 1);
+        assert_eq!(collision_step_count(FGi32::lit("6.01")), 2);
+        assert_eq!(collision_step_count(FGi32::lit("12")), 3);
+        assert_eq!(collision_step_count(FGi32::lit("18")), 4);
+    }
+
+    #[test]
+    fn collision_result_keeps_ecb_local_to_resolved_origin() {
+        let stage_collision = StageCollision {
+            stage_polys: vec![horizontal_platform("0")],
+            ..StageCollision::default()
+        };
+        let previous_translation = FighterPreviousTranslation(FGVec2::lit("0", "2"));
+        let mut translation = FighterTranslation(FGVec2::lit("0", "-1"));
+        let mut velocity = FighterVelocity(FGVec2::lit("0", "-3"));
+        let mut ecb = FighterECB {
+            top: FGVec2::lit("0", "2"),
+            bottom: FGVec2::lit("0", "-1"),
+            left: FGVec2::lit("-1", "0.5"),
+            right: FGVec2::lit("1", "0.5"),
+        };
+        let desired = FighterDesiredECB::from(ecb);
+        let collision = air_collide_with_stage_substepped(
+            &previous_translation,
+            &mut translation,
+            &mut velocity,
+            &mut ecb,
+            &desired,
+            &stage_collision,
+            &[],
+            Default::default(),
+        )
+        .expect("the floor should be hit");
+
+        assert_eq!(
+            collision.resolved_translation + ecb.bottom,
+            collision.hit_position
+        );
+        assert_eq!(velocity.0.y, FGi32::ZERO);
+    }
+
+    #[test]
+    fn airborne_side_point_resolves_wall_and_projects_velocity() {
+        let stage_collision = StageCollision {
+            stage_polys: vec![single_segment(
+                FGVec2::lit("2", "2"),
+                FGVec2::lit("2", "-2"),
+                StagePolyLineSegmentType::Wall,
+            )],
+            ..StageCollision::default()
+        };
+        let previous = FighterPreviousTranslation(FGVec2::lit("4", "0"));
+        let mut translation = FighterTranslation(FGVec2::lit("0", "0"));
+        let mut velocity = FighterVelocity(FGVec2::lit("-4", "0"));
+        let mut ecb = FighterECB {
+            top: FGVec2::lit("0", "1"),
+            bottom: FGVec2::lit("0", "-1"),
+            left: FGVec2::lit("-1", "0"),
+            right: FGVec2::lit("1", "0"),
+        };
+        let desired = FighterDesiredECB::from(ecb);
+
+        assert!(air_collide_with_stage_substepped(
+            &previous,
+            &mut translation,
+            &mut velocity,
+            &mut ecb,
+            &desired,
+            &stage_collision,
+            &[],
+            Default::default(),
+        )
+        .is_none());
+        assert_eq!(translation.0, FGVec2::lit("3", "0"));
+        assert_eq!(velocity.0.x, FGi32::ZERO);
+    }
+
+    #[test]
+    fn stage_corner_cannot_pass_through_middle_of_diamond_edge() {
+        let stage_collision = StageCollision {
+            stage_polys: vec![single_segment(
+                FGVec2::lit("2", "0.6"),
+                FGVec2::lit("2", "0.4"),
+                StagePolyLineSegmentType::Wall,
+            )],
+            ..StageCollision::default()
+        };
+        let previous = FighterPreviousTranslation(FGVec2::lit("4", "0"));
+        let mut translation = FighterTranslation(FGVec2::ZERO);
+        let mut velocity = FighterVelocity(FGVec2::lit("-4", "0"));
+        let mut ecb = FighterECB {
+            top: FGVec2::lit("0", "1"),
+            bottom: FGVec2::lit("0", "-1"),
+            left: FGVec2::lit("-1", "0"),
+            right: FGVec2::lit("1", "0"),
+        };
+        let desired = FighterDesiredECB::from(ecb);
+
+        assert!(air_collide_with_stage_substepped(
+            &previous,
+            &mut translation,
+            &mut velocity,
+            &mut ecb,
+            &desired,
+            &stage_collision,
+            &[],
+            Default::default(),
+        )
+        .is_none());
+        assert_eq!(translation.0.x, FGi32::lit("3"));
+        assert_eq!(velocity.0.x, FGi32::ZERO);
+    }
+
+    #[test]
+    fn airborne_top_point_resolves_ceiling_and_projects_velocity() {
+        let stage_collision = StageCollision {
+            stage_polys: vec![single_segment(
+                FGVec2::lit("2", "2"),
+                FGVec2::lit("-2", "2"),
+                StagePolyLineSegmentType::Ceiling,
+            )],
+            ..StageCollision::default()
+        };
+        let previous = FighterPreviousTranslation(FGVec2::ZERO);
+        let mut translation = FighterTranslation(FGVec2::lit("0", "4"));
+        let mut velocity = FighterVelocity(FGVec2::lit("0", "4"));
+        let mut ecb = FighterECB {
+            top: FGVec2::lit("0", "1"),
+            bottom: FGVec2::lit("0", "-1"),
+            left: FGVec2::lit("-1", "0"),
+            right: FGVec2::lit("1", "0"),
+        };
+        let desired = FighterDesiredECB::from(ecb);
+
+        assert!(air_collide_with_stage_substepped(
+            &previous,
+            &mut translation,
+            &mut velocity,
+            &mut ecb,
+            &desired,
+            &stage_collision,
+            &[],
+            Default::default(),
+        )
+        .is_none());
+        assert_eq!(translation.0, FGVec2::lit("0", "1"));
+        assert_eq!(velocity.0.y, FGi32::ZERO);
+    }
+
     #[test]
     fn airborne_collision_skips_ignored_polygons() {
         let stage_collision = StageCollision {
             stage_polys: vec![horizontal_platform("0"), horizontal_platform("1")],
+            ..StageCollision::default()
         };
         let previous_translation = FighterPreviousTranslation(FGVec2::lit("0", "2"));
         let translation = FighterTranslation(FGVec2::lit("0", "-1"));
@@ -138,7 +670,7 @@ mod tests {
             &ecb,
             &stage_collision,
             &[1],
-            false,
+            Default::default(),
         )
         .expect("the non-ignored platform should still be collidable");
 
@@ -150,6 +682,7 @@ mod tests {
     fn airborne_collision_skips_soft_platforms_while_passing_down() {
         let stage_collision = StageCollision {
             stage_polys: vec![horizontal_platform("0")],
+            ..StageCollision::default()
         };
         let previous_translation = FighterPreviousTranslation(FGVec2::lit("0", "2"));
         let translation = FighterTranslation(FGVec2::lit("0", "-1"));
@@ -166,16 +699,21 @@ mod tests {
             right: FGVec2::ZERO,
         };
 
-        assert!(air_collide_with_stage(
+        assert!(
-            &previous_translation,
+            air_collide_with_stage(
-            &translation,
+                &previous_translation,
-            &previous_ecb,
+                &translation,
-            &ecb,
+                &previous_ecb,
-            &stage_collision,
+                &ecb,
-            &[],
+                &stage_collision,
-            true,
+                &[],
-        )
+                AirCollisionOptions {
-        .is_none());
+                    can_pass_through_soft_platforms: true,
+                    ..Default::default()
+                },
+            )
+            .is_none()
+        );
 
         assert_eq!(
             air_collide_with_stage(
@@ -185,7 +723,7 @@ mod tests {
                 &ecb,
                 &stage_collision,
                 &[],
-                false,
+                Default::default(),
             )
             .expect("air dodges still collide with soft platforms")
             .hit_position,
@@ -197,6 +735,7 @@ mod tests {
     fn airborne_collision_still_hits_solid_floors_while_passing_down() {
         let stage_collision = StageCollision {
             stage_polys: vec![solid_floor()],
+            ..StageCollision::default()
         };
         let previous_translation = FighterPreviousTranslation(FGVec2::lit("0", "2"));
         let translation = FighterTranslation(FGVec2::lit("0", "-1"));
@@ -220,11 +759,131 @@ mod tests {
             &ecb,
             &stage_collision,
             &[],
-            true,
+            AirCollisionOptions {
+                can_pass_through_soft_platforms: true,
+                ..Default::default()
+            },
         )
         .expect("solid floors remain collidable while passing down");
 
         assert_eq!(collision.line_id.polygon, 0);
         assert_eq!(collision.hit_position, FGVec2::lit("0", "0"));
     }
+
+    #[test]
+    fn upward_bottom_crossing_can_land_on_soft_platform() {
+        let stage_collision = StageCollision {
+            stage_polys: vec![horizontal_platform("0")],
+            ..Default::default()
+        };
+        let previous_translation = FighterPreviousTranslation(FGVec2::lit("0", "-1"));
+        let mut translation = FighterTranslation(FGVec2::lit("0", "1"));
+        let mut velocity = FighterVelocity(FGVec2::lit("0", "2"));
+        let mut ecb = FighterECB::default();
+        let desired = FighterDesiredECB::from(ecb);
+
+        let collision = air_collide_with_stage_substepped(
+            &previous_translation,
+            &mut translation,
+            &mut velocity,
+            &mut ecb,
+            &desired,
+            &stage_collision,
+            &[],
+            AirCollisionOptions {
+                land_on_soft_platforms_from_below: true,
+                ..Default::default()
+            },
+        )
+        .expect("the upward bottom-point crossing should land on the platform");
+
+        assert_eq!(collision.hit_position, FGVec2::ZERO);
+        assert_eq!(collision.line_id, StageLineID { polygon: 0, segment: 0 });
+        assert_eq!(translation.0, FGVec2::ZERO);
+        assert_eq!(velocity.y, FGi32::ZERO);
+    }
+
+    #[test]
+    fn upward_platform_landing_requires_crossing_and_opt_in() {
+        let stage_collision = StageCollision {
+            stage_polys: vec![horizontal_platform("0")],
+            ..Default::default()
+        };
+        let previous_ecb = FighterPreviousECB::default();
+        let ecb = FighterECB::default();
+        let options = AirCollisionOptions {
+            land_on_soft_platforms_from_below: true,
+            ..Default::default()
+        };
+
+        assert!(
+            air_collide_with_stage(
+                &FighterPreviousTranslation(FGVec2::lit("0", "-2")),
+                &FighterTranslation(FGVec2::lit("0", "-1")),
+                &previous_ecb,
+                &ecb,
+                &stage_collision,
+                &[],
+                options,
+            )
+            .is_none()
+        );
+        assert!(
+            air_collide_with_stage(
+                &FighterPreviousTranslation(FGVec2::lit("0", "-1")),
+                &FighterTranslation(FGVec2::lit("0", "1")),
+                &previous_ecb,
+                &ecb,
+                &stage_collision,
+                &[],
+                Default::default(),
+            )
+            .is_none()
+        );
+    }
+
+    #[test]
+    fn upward_crossing_does_not_land_on_solid_or_ignored_platforms() {
+        let previous_translation = FighterPreviousTranslation(FGVec2::lit("0", "-1"));
+        let translation = FighterTranslation(FGVec2::lit("0", "1"));
+        let previous_ecb = FighterPreviousECB::default();
+        let ecb = FighterECB::default();
+        let options = AirCollisionOptions {
+            land_on_soft_platforms_from_below: true,
+            ..Default::default()
+        };
+        let solid_stage = StageCollision {
+            stage_polys: vec![solid_floor()],
+            ..Default::default()
+        };
+        let platform_stage = StageCollision {
+            stage_polys: vec![horizontal_platform("0")],
+            ..Default::default()
+        };
+
+        assert!(
+            air_collide_with_stage(
+                &previous_translation,
+                &translation,
+                &previous_ecb,
+                &ecb,
+                &solid_stage,
+                &[],
+                options,
+            )
+            .is_none()
+        );
+        assert!(
+            air_collide_with_stage(
+                &previous_translation,
+                &translation,
+                &previous_ecb,
+                &ecb,
+                &platform_stage,
+                &[0],
+                options,
+            )
+            .is_none()
+        );
+    }
 }

src/fighter/debug.rs

@@ -216,6 +216,26 @@ pub fn hurtbox_debug(
     }
 }
 
+pub fn ledge_grab_debug(query: Query<(&FighterTranslation, &Fighter)>, fighters: Res<Assets<FighterManifest>>, mut gizmos: Gizmos) {
+    for (translation, fighter) in query {
+        let Some(manifest) = fighters.get(&fighter.manifest) else {
+            continue;
+        };
+
+        let start_2d = translation.0 + manifest.ledge_grab_box_start;
+        let start_2d = Vec2::new(start_2d.x.to_num(), start_2d.y.to_num());
+
+        let end_2d = translation.0 + manifest.ledge_grab_box_end;
+        let end_2d = Vec2::new(end_2d.x.to_num(), end_2d.y.to_num());
+
+
+        let center = (start_2d + end_2d) * 0.5;
+        let size = (start_2d - end_2d).abs();
+        
+        gizmos.rect(Vec3::new(center.x, center.y, 0.0), size, bevy::color::palettes::css::BLUE);
+    }
+}
+
 /*fn draw_affine_capsule(
     gizmos: &mut Gizmos,
     capsule: FixedAffineCapsule,

src/fighter/ecb.rs

@@ -4,14 +4,12 @@ use crate::{
     fighter::{
         FighterFacingDirection, FighterSurfaceState, FighterTranslation,
         baked_animation::FighterBoneMatrices,
-    }, math::{int::FGi32, vec::FGVec2},
+    },
+    math::{int::FGi32, vec::FGVec2},
 };
 
-/// Environment collision box: the diamond used to resolve a fighter against
-/// the stage. Purely geometry — the collision response lives in
-/// [`super::collision`].
 #[derive(Component, Debug, Clone, Copy, Hash, Default)]
-#[require(FighterPreviousECB)]
+#[require(FighterPreviousECB, FighterDesiredECB)]
 pub struct FighterECB {
     pub top: FGVec2,
     pub bottom: FGVec2,
@@ -19,6 +17,14 @@ pub struct FighterECB {
     pub right: FGVec2,
 }
 
+#[derive(Component, Debug, Clone, Copy, Hash, Default)]
+pub struct FighterDesiredECB {
+    pub top: FGVec2,
+    pub bottom: FGVec2,
+    pub left: FGVec2,
+    pub right: FGVec2,
+}
+
 #[derive(Component, Debug, Clone)]
 pub struct FighterECBBoneIndices {
     pub indices: Vec<usize>,
@@ -43,12 +49,96 @@ impl From<FighterECB> for FighterPreviousECB {
     }
 }
 
+impl From<FighterECB> for FighterDesiredECB {
+    fn from(ecb: FighterECB) -> Self {
+        Self {
+            top: ecb.top,
+            bottom: ecb.bottom,
+            left: ecb.left,
+            right: ecb.right,
+        }
+    }
+}
+
+impl FighterDesiredECB {
+    pub fn as_ecb(self) -> FighterECB {
+        FighterECB {
+            top: self.top,
+            bottom: self.bottom,
+            left: self.left,
+            right: self.right,
+        }
+    }
+
+    pub fn validate(&mut self) {
+        let minimum = FGi32::lit("1.0");
+        if (self.top.y - self.bottom.y).abs() < minimum {
+            self.top.y += minimum;
+            let midpoint = (self.top.y + self.bottom.y) / FGi32::lit("2.0");
+            self.left.y = midpoint;
+            self.right.y = midpoint;
+        }
+        if self.top.y < minimum {
+            self.top.y = minimum;
+        }
+        if self.left.x > -minimum {
+            self.left.x = -minimum;
+        }
+        if self.right.x < minimum {
+            self.right.x = minimum;
+        }
+        if self.top.y < self.bottom.y {
+            self.top.y = self.bottom.y + minimum;
+        }
+
+        let midpoint = (self.top.y + self.bottom.y) / FGi32::lit("2.0");
+        if self.left.y < self.bottom.y || self.left.y > self.top.y {
+            self.left.y = midpoint;
+        }
+        if self.right.y < self.bottom.y || self.right.y > self.top.y {
+            self.left.y = midpoint;
+            self.right.y = midpoint;
+        }
+        let epsilon = FGi32::from_bits(66);
+        if self.top.y - self.right.y < epsilon
+            || self.right.y - self.bottom.y < epsilon
+        {
+            self.right.y = midpoint;
+        }
+        if self.top.y - self.left.y < epsilon
+            || self.left.y - self.bottom.y < epsilon
+        {
+            self.left.y = midpoint;
+        }
+    }
+}
+
 pub fn snapshot_fighter_ecb(fighters: Query<(&FighterECB, &mut FighterPreviousECB)>) {
     for (ecb, mut previous_ecb) in fighters {
         *previous_ecb = (*ecb).into();
     }
 }
 
+pub fn interpolate_ecb(ecb: &mut FighterECB, desired: FighterDesiredECB, time: FGi32) {
+    let lerp = |a: FGVec2, b: FGVec2| a + (b - a) * time;
+    ecb.top = lerp(ecb.top, desired.top);
+    ecb.bottom = lerp(ecb.bottom, desired.bottom);
+    ecb.left = lerp(ecb.left, desired.left);
+    ecb.right = lerp(ecb.right, desired.right);
+}
+
+pub fn ecb_max_delta(ecb: &FighterECB, desired: &FighterDesiredECB) -> FGi32 {
+    [
+        (desired.left.x - ecb.left.x).abs(),
+        (desired.right.x - ecb.right.x).abs(),
+        (desired.top.y - ecb.top.y).abs(),
+        (desired.right.y - ecb.right.y).abs(),
+    ]
+    .into_iter()
+    .max()
+    .unwrap_or(FGi32::ZERO)
+}
+
 impl FighterECB {
     pub fn to_3d_lineloop(&self, trf: Transform) -> [Vec3; 4] {
         [self.top, self.right, self.bottom, self.left]
@@ -58,6 +148,17 @@ impl FighterECB {
     pub fn get_bottom_point(&self) -> FGVec2 {
         self.bottom
     }
+
+    /// Change the local origin to the bottom point without moving the ECB in
+    /// world space. Grounded fighters use the floor contact as their origin.
+    pub fn rebase_onto_bottom(&mut self) -> FGVec2 {
+        let bottom = self.bottom;
+        self.top -= bottom;
+        self.left -= bottom;
+        self.right -= bottom;
+        self.bottom = FGVec2::ZERO;
+        bottom
+    }
 }
 
 impl FighterPreviousECB {
@@ -73,7 +174,7 @@ impl FighterPreviousECB {
 
 pub fn update_ecb(
     query: Query<(
-        &mut FighterECB,
+        &mut FighterDesiredECB,
         &FighterSurfaceState,
         &FighterECBBoneIndices,
         &FighterBoneMatrices,
@@ -81,23 +182,44 @@ pub fn update_ecb(
         &FighterFacingDirection,
     )>,
 ) {
-    for (mut ecb, surface_state, bone_indices, bone_matrices, translation, facing_dir) in query {
+    for (mut desired, surface_state, bone_indices, bone_matrices, translation, facing_dir) in query
+    {
         let trf = translation.get_3d_transform(facing_dir);
 
-        let transformed_ecb_bones = bone_indices.indices.iter().filter_map(|idx| {
+        let transformed_ecb_bones = bone_indices
-            let Some((_, bone_matrix)) = bone_matrices.get_by_idx(*idx) else {
+            .indices
-                return None;
+            .iter()
-            };
+            .filter_map(|idx| {
+                let Some((_, bone_matrix)) = bone_matrices.get_by_idx(*idx) else {
+                    return None;
+                };
 
-            let pt = trf.transform_point(bone_matrix.get_translation());
+                let pt = trf.transform_point(bone_matrix.get_translation());
 
-            Some(FGVec2::new(pt.x, pt.y) - translation.0)
+                Some(FGVec2::new(pt.x, pt.y) - translation.0)
-        }).collect::<Vec<_>>();
+            })
+            .collect::<Vec<_>>();
 
-        let max_x = transformed_ecb_bones.iter().max_by(|a, b| a.x.cmp(&b.x)).map(|final_val| final_val.x).unwrap_or(FGi32::lit("0.5"));
+        let max_x = transformed_ecb_bones
-        let min_x = transformed_ecb_bones.iter().min_by(|a, b| a.x.cmp(&b.x)).map(|final_val| final_val.x).unwrap_or(FGi32::lit("-0.5"));
+            .iter()
-        let max_y = transformed_ecb_bones.iter().max_by(|a, b| a.y.cmp(&b.y)).map(|final_val| final_val.y).unwrap_or(FGi32::lit("0.5"));
+            .max_by(|a, b| a.x.cmp(&b.x))
-        let min_y = transformed_ecb_bones.iter().min_by(|a, b| a.y.cmp(&b.y)).map(|final_val| final_val.y).unwrap_or(FGi32::lit("-0.5"));
+            .map(|final_val| final_val.x)
+            .unwrap_or(FGi32::lit("0.5"));
+        let min_x = transformed_ecb_bones
+            .iter()
+            .min_by(|a, b| a.x.cmp(&b.x))
+            .map(|final_val| final_val.x)
+            .unwrap_or(FGi32::lit("-0.5"));
+        let max_y = transformed_ecb_bones
+            .iter()
+            .max_by(|a, b| a.y.cmp(&b.y))
+            .map(|final_val| final_val.y)
+            .unwrap_or(FGi32::lit("0.5"));
+        let min_y = transformed_ecb_bones
+            .iter()
+            .min_by(|a, b| a.y.cmp(&b.y))
+            .map(|final_val| final_val.y)
+            .unwrap_or(FGi32::lit("-0.5"));
 
         let midpoint_height = (max_y + min_y) / FGi32::lit("2.0");
         let top = FGVec2::new(FGi32::ZERO, max_y);
@@ -105,24 +227,29 @@ pub fn update_ecb(
         let left = FGVec2::new(min_x, midpoint_height);
         let right = FGVec2::new(max_x, midpoint_height);
 
-        let ecb_lock_frames_remaining = if let FighterSurfaceState::Airborne { ecb_lock_frames_remaining, .. } = surface_state {
+        let ecb_lock_frames_remaining = if let FighterSurfaceState::Airborne {
+            ecb_lock_frames_remaining,
+            ..
+        } = surface_state
+        {
             *ecb_lock_frames_remaining
         } else {
             0
         };
 
-        ecb.top = top;
+        desired.top = top;
 
         if ecb_lock_frames_remaining == 0 {
-            ecb.bottom = bottom;
+            desired.bottom = bottom;
         }
 
-        ecb.left = left;
+        desired.left = left;
-        ecb.right = right;
+        desired.right = right;
 
         if surface_state.is_grounded() {
-            ecb.bottom = FGVec2::ZERO;
+            desired.bottom = FGVec2::ZERO;
         }
+        desired.validate();
     }
 }
 
@@ -152,4 +279,60 @@ mod tests {
         assert_eq!(previous.left, current.left);
         assert_eq!(previous.right, current.right);
     }
+
+    #[test]
+    fn interpolation_reaches_target_with_full_step() {
+        let mut current = FighterECB {
+            top: FGVec2::lit("0", "1"),
+            bottom: FGVec2::lit("0", "0"),
+            left: FGVec2::lit("-1", "0.5"),
+            right: FGVec2::lit("1", "0.5"),
+        };
+        let desired = FighterDesiredECB {
+            top: FGVec2::lit("0", "3"),
+            bottom: FGVec2::lit("0", "-1"),
+            left: FGVec2::lit("-2", "1"),
+            right: FGVec2::lit("2", "1"),
+        };
+        interpolate_ecb(&mut current, desired, FGi32::ONE);
+        assert_eq!(current.top, desired.top);
+        assert_eq!(current.bottom, desired.bottom);
+        assert_eq!(current.left, desired.left);
+        assert_eq!(current.right, desired.right);
+    }
+
+    #[test]
+    fn validation_repairs_tiny_and_out_of_range_diamond() {
+        let mut desired = FighterDesiredECB {
+            top: FGVec2::lit("0", "0.25"),
+            bottom: FGVec2::lit("0", "0"),
+            left: FGVec2::lit("0", "4"),
+            right: FGVec2::lit("0", "-4"),
+        };
+        desired.validate();
+
+        assert_eq!(desired.top.y, FGi32::lit("1.25"));
+        assert_eq!(desired.left.x, FGi32::lit("-1"));
+        assert_eq!(desired.right.x, FGi32::lit("1"));
+        assert_eq!(desired.left.y, FGi32::lit("0.625"));
+        assert_eq!(desired.right.y, FGi32::lit("0.625"));
+    }
+
+    #[test]
+    fn rebasing_onto_bottom_preserves_world_points() {
+        let origin = FGVec2::lit("4", "8");
+        let mut ecb = FighterECB {
+            top: FGVec2::lit("0", "3"),
+            bottom: FGVec2::lit("0", "-1"),
+            left: FGVec2::lit("-2", "1"),
+            right: FGVec2::lit("2", "1"),
+        };
+        let old_world_points = [ecb.top, ecb.bottom, ecb.left, ecb.right].map(|p| origin + p);
+        let new_origin = origin + ecb.bottom;
+        ecb.rebase_onto_bottom();
+        let new_world_points = [ecb.top, ecb.bottom, ecb.left, ecb.right].map(|p| new_origin + p);
+
+        assert_eq!(old_world_points, new_world_points);
+        assert_eq!(ecb.bottom, FGVec2::ZERO);
+    }
 }

src/fighter/manifest.rs

@@ -8,11 +8,7 @@ use strum::IntoEnumIterator;
 use strum_macros::EnumIter;
 
 use crate::{
-    AppState,
+    AppState, fighter::{FighterAttributes, FighterCameraProfile, animation::AnimKind, attack::AttackKind}, game_settings::GameSettings, math::{int::FGi32, vec::FGVec2, vec3::FGVec3}, texture_reference::TextureReference,
-    fighter::{FighterAttributes, FighterCameraProfile, animation::AnimKind, attack::AttackKind},
-    game_settings::GameSettings,
-    math::{int::FGi32, vec3::FGVec3},
-    texture_reference::TextureReference,
 };
 
 #[derive(
@@ -69,6 +65,8 @@ pub struct FighterManifest {
     pub attack_scripts: HashMap<AttackKind, String>,
     pub hurtboxes: Vec<FighterHurtbox>,
     pub ecb_bones: Vec<String>,
+    pub ledge_grab_box_start: FGVec2,
+    pub ledge_grab_box_end: FGVec2,
 }
 
 fn default_root_motion_bone() -> String {

src/fighter/mod.rs

@@ -10,6 +10,7 @@ pub mod animation;
 pub mod attack;
 pub mod attributes;
 pub mod baked_animation;
+pub mod blast_zones;
 pub mod collision;
 pub mod debug;
 pub mod ecb;
@@ -21,7 +22,6 @@ pub mod push;
 pub mod state;
 pub mod surface;
 pub mod visual;
-pub mod blast_zones;
 
 // The fighter components are re-exported so the rest of the crate can say
 // `fighter::FighterVelocity` without caring which file it lives in. Named
@@ -37,13 +37,25 @@ pub use motion::{
 pub use surface::FighterSurfaceState;
 
 use crate::{
-    AppState, fighter::{
+    AppState,
+    fighter::{
         attack::{
             AttackKind, FighterAttackPlugin, FighterAttackScriptAssets, FighterDamage,
-            FighterKnockbackVelocity, FighterPendingHitReaction, FighterSolvedHurtboxes,
+            FighterKnockbackState, FighterKnockbackVelocity, FighterPendingHitReaction,
-            FighterStaleMoveQueue,
+            FighterSolvedHurtboxes, FighterStaleMoveQueue,
-        }, baked_animation::FighterBoneIndexMap, ecb::FighterECBBoneIndices, manifest::FighterManifest, state::{FighterState, air::AirborneStateCommon, fall::FallState}, visual::{FighterAnimations, FighterInvulnerabilityVisualState},
+        },
-    }, game_settings::GameSettings, input::FighterInput, math::{int::FGi32, vec::FGVec2}, player::Player, schedule::GameplaySet, scripting::FighterAttackScript,
+        baked_animation::FighterBoneIndexMap,
+        ecb::{FighterDesiredECB, FighterECBBoneIndices},
+        manifest::FighterManifest,
+        state::{FighterState, air::AirborneStateCommon, fall::FallState},
+        visual::{FighterAnimations, FighterInvulnerabilityVisualState},
+    },
+    game_settings::GameSettings,
+    input::FighterInput,
+    math::{int::FGi32, vec::FGVec2},
+    player::Player,
+    schedule::GameplaySet,
+    scripting::FighterAttackScript,
 };
 use state::state_interrupt_system;
 
@@ -86,12 +98,62 @@ pub struct FighterHitstop {
     pub remaining_frames: u32,
 }
 
+#[derive(Component, Default, Copy, Clone, Hash, Debug, PartialEq, Eq)]
+pub struct FighterLedgeInformation {
+    pub regrab_lockout_remaining_frames: u32,
+    pub grab_count: u32,
+}
+
+impl FighterLedgeInformation {
+    pub fn start(&mut self, duration_frames: u32) {
+        self.regrab_lockout_remaining_frames = duration_frames;
+    }
+
+    pub fn is_regrab_lockout_active(&self) -> bool {
+        self.regrab_lockout_remaining_frames > 0
+    }
+
+    fn tick(&mut self) {
+        self.regrab_lockout_remaining_frames =
+            self.regrab_lockout_remaining_frames.saturating_sub(1);
+    }
+}
+
+#[cfg(test)]
+mod ledge_grab_lockout_tests {
+    use super::FighterLedgeInformation;
+
+    #[test]
+    fn lockout_expires_after_the_requested_number_of_ticks() {
+        let mut lockout = FighterLedgeInformation::default();
+        lockout.start(2);
+
+        assert!(lockout.is_regrab_lockout_active());
+        lockout.tick();
+        assert!(lockout.is_regrab_lockout_active());
+        lockout.tick();
+        assert!(!lockout.is_regrab_lockout_active());
+    }
+
+    #[test]
+    fn zero_duration_does_not_enable_lockout() {
+        let mut lockout = FighterLedgeInformation::default();
+        lockout.start(0);
+
+        assert!(!lockout.is_regrab_lockout_active());
+    }
+}
+
 #[derive(Component, Default, Copy, Clone, Hash)]
 pub enum FighterInvulnerabilityState {
     #[default]
     Vulnerable,
-    Invulnerable { frames_remaining: Option<u32> },
+    Invulnerable {
-    Intangible { frames_remaining: Option<u32> }
+        frames_remaining: Option<u32>,
+    },
+    Intangible {
+        frames_remaining: Option<u32>,
+    },
 }
 
 impl FighterFacingDirection {
@@ -148,10 +210,12 @@ pub struct FighterPendingRespawn(bool);
     FighterPendingHitReaction,
     FighterPendingRespawn,
     FighterHitstop,
+    FighterLedgeInformation,
     FighterKnockbackVelocity,
+    FighterKnockbackState,
     FighterTranslation,
     FighterInvulnerabilityState,
-    FighterInvulnerabilityVisualState,
+    FighterInvulnerabilityVisualState
 )]
 pub struct Fighter {
     pub manifest: Handle<FighterManifest>,
@@ -180,7 +244,10 @@ impl Plugin for FighterPlugin {
             )
             .add_systems(
                 GgrsSchedule,
-                (state::state_update_system, decay_hitstop, decay_invulnerability)
+                (
+                    state::state_update_system,
+                    decay_invulnerability,
+                )
                     .chain()
                     .in_set(GameplaySet::StateUpdate),
             )
@@ -193,7 +260,16 @@ impl Plugin for FighterPlugin {
             .add_systems(
                 GgrsSchedule,
                 (
-                    (blast_zones::apply_blast_zones, ecb::update_ecb, ecb::decrement_ecb_lockout, state::state_collision_interrupt_system).chain(),
+                    (
+                        blast_zones::apply_blast_zones,
+                        ecb::decrement_ecb_lockout,
+                        ecb::update_ecb,
+                        state::state_collision_interrupt_system,
+                        // Every gameplay phase must observe the same hitstop value.
+                        decay_hitstop,
+                        decay_ledge_grab_lockout,
+                    )
+                        .chain(),
                     baked_animation::resample_fighter_bone_matrices,
                 )
                     .chain()
@@ -220,6 +296,8 @@ impl Plugin for FighterPlugin {
             // is a desync waiting to happen.
             .rollback_component_with_copy::<FighterECB>()
             .checksum_component_with_hash::<FighterECB>()
+            .rollback_component_with_copy::<FighterDesiredECB>()
+            .checksum_component_with_hash::<FighterDesiredECB>()
             .rollback_component_with_clone::<FighterStaleMoveQueue>()
             .checksum_component_with_hash::<FighterStaleMoveQueue>()
             .rollback_component_with_copy::<ecb::FighterPreviousECB>()
@@ -247,10 +325,14 @@ impl Plugin for FighterPlugin {
             .checksum_component_with_hash::<FighterPendingRespawn>()
             .rollback_component_with_copy::<FighterHitstop>()
             .checksum_component_with_hash::<FighterHitstop>()
+            .rollback_component_with_copy::<FighterLedgeInformation>()
+            .checksum_component_with_hash::<FighterLedgeInformation>()
             .rollback_component_with_copy::<FighterInvulnerabilityState>()
             .checksum_component_with_hash::<FighterInvulnerabilityState>()
             .rollback_component_with_copy::<FighterKnockbackVelocity>()
             .checksum_component_with_hash::<FighterKnockbackVelocity>()
+            .rollback_component_with_copy::<FighterKnockbackState>()
+            .checksum_component_with_hash::<FighterKnockbackState>()
             .rollback_component_with_clone::<baked_animation::FighterBoneMatrices>()
             .checksum_component_with_hash::<baked_animation::FighterBoneMatrices>()
             // Debug views.
@@ -258,6 +340,10 @@ impl Plugin for FighterPlugin {
                 FixedPostUpdate,
                 debug::debug_draw_ecb.run_if(crate::debug_tools::ecb_enabled),
             )
+            .add_systems(
+                FixedPostUpdate,
+                debug::ledge_grab_debug.run_if(crate::debug_tools::ledge_grab_enabled),
+            )
             .add_systems(
                 EguiPrimaryContextPass,
                 debug::fighter_debug.run_if(crate::debug_tools::fighter_info_enabled),
@@ -277,8 +363,9 @@ impl Plugin for FighterPlugin {
                     .run_if(crate::debug_tools::attack_hitboxes_enabled)
                     .run_if(in_state(AppState::InMatch)),
             )
-            .add_systems(FixedPostUpdate, 
+            .add_systems(
-                visual::update_status_colors.run_if(resource_exists::<GameSettings>)
+                FixedPostUpdate,
+                visual::update_status_colors.run_if(resource_exists::<GameSettings>),
             )
             .add_systems(
                 FixedPostUpdate,
@@ -338,10 +425,11 @@ pub fn spawn_fighter(
             Transform::from_scale(Vec3::splat(model_scale.to_num())),
             (
                 FighterECB::default(),
+                FighterDesiredECB::default(),
                 FighterHitboxes::default(),
                 FighterECBBoneIndices {
-                    indices: ecb_bone_indices
+                    indices: ecb_bone_indices,
-                }
+                },
             ),
             (
                 FighterVelocity::default(),
@@ -373,6 +461,12 @@ pub fn decay_hitstop(query: Query<(&mut FighterHitstop, &mut FighterHitstopShake
     }
 }
 
+pub fn decay_ledge_grab_lockout(query: Query<&mut FighterLedgeInformation>) {
+    for mut lockout in query {
+        lockout.tick();
+    }
+}
+
 pub fn decay_invulnerability(query: Query<&mut FighterInvulnerabilityState>) {
     for invuln_state in query {
         let invuln_state = invuln_state.into_inner();
@@ -385,7 +479,7 @@ pub fn decay_invulnerability(query: Query<&mut FighterInvulnerabilityState>) {
                 } else {
                     None
                 }
-            },
+            }
             FighterInvulnerabilityState::Intangible { frames_remaining } => {
                 if let Some(frames_remaining) = frames_remaining {
                     *frames_remaining = frames_remaining.saturating_sub(1);
@@ -393,7 +487,7 @@ pub fn decay_invulnerability(query: Query<&mut FighterInvulnerabilityState>) {
                 } else {
                     None
                 }
-            },
+            }
         };
 
         if let Some(frames_remaining) = frames_remaining {

src/fighter/push.rs

@@ -134,6 +134,7 @@ mod tests {
                     (FGVec2::lit("30", "0"), StagePolyLineSegmentType::Floor),
                 ],
             )],
+            ..StageCollision::default()
         }
     }
 

src/fighter/state/air.rs

@@ -1,5 +1,6 @@
 use crate::fighter::state::jump::{self};
 use crate::fighter::state::land::{LandingState, LandingType};
+use crate::fighter::state::ledge_grab::LedgeGrabState;
 use crate::fighter::state::{
     CollisionContext, FighterState, InterruptContext, air_attack, air_dodge,
 };
@@ -92,6 +93,19 @@ pub fn apply_air_motion(
     translation.0 += velocity.0;
 }
 
+/// Applies ordinary and launch velocity together, then advances launch decay.
+/// Hitstop skips state updates entirely, so neither decay nor launch age moves
+/// while the fighter is frozen.
+pub fn apply_air_motion_with_knockback(ctx: &mut crate::fighter::state::UpdateContext) {
+    let combined_velocity = FighterVelocity(ctx.velocity.0 + ctx.knockback_velocity.0);
+    apply_air_motion(&combined_velocity, ctx.translation, ctx.prev_translation);
+    attack::decay_knockback(
+        ctx.knockback_velocity,
+        ctx.knockback_state,
+        ctx.game_settings.fighter_common.knockback_decay_per_frame,
+    );
+}
+
 pub fn update_standard_motion(
     ctx: &mut crate::fighter::state::UpdateContext,
     airborne_common: &mut AirborneStateCommon,
@@ -108,7 +122,7 @@ pub fn update_standard_motion(
         airborne_common.is_fast_falling,
     );
     apply_air_drift(ctx.velocity, ctx.fighter_attributes, ctx.input);
-    apply_air_motion(ctx.velocity, ctx.translation, ctx.prev_translation);
+    apply_air_motion_with_knockback(ctx);
 }
 
 pub fn air_interrupts_common(
@@ -124,17 +138,24 @@ pub fn air_interrupts_common(
 pub fn collision_interrupt(
     ctx: &mut CollisionContext,
     landing_type: LandingType,
-    can_ignore_soft_platforms: bool,
+    options: crate::fighter::collision::AirCollisionOptions,
 ) -> Option<FighterState> {
-    let res = ctx.air_collide_with_stage(can_ignore_soft_platforms)?;
+    if ctx.velocity.y <= FGi32::ZERO {
-    let diff = res.hit_position - ctx.translation.0;
+        if let Some(ledge_result) = ctx.air_collide_with_ledges() {
-    ctx.ecb.bottom -= diff;
+            ctx.apply_desired_ecb();
-    ctx.ecb.top -= diff;
+            return Some(FighterState::LedgeGrab(LedgeGrabState::new(ledge_result.ledge)));
-    ctx.ecb.left -= diff;
+        }
-    ctx.ecb.right -= diff;
+    }
-    ctx.translation.0 = res.hit_position;
+
+    let res = ctx.air_collide_with_stage(options)?;
+    ctx.translation.0 = res.resolved_translation;
+    let bottom_offset = ctx.ecb.rebase_onto_bottom();
+    ctx.translation.0 += bottom_offset;
+    *ctx.desired_ecb = crate::fighter::ecb::FighterDesiredECB::from(*ctx.ecb);
     ctx.presentation_snap.0 = true;
-    ctx.surface.land(res.line_id);
+    ctx.surface.land(res.line_id, ctx.ledge_info);
+    ctx.knockback_velocity.0 = FGVec2::ZERO;
+    ctx.knockback_state.clear();
     Some(FighterState::Land(LandingState::create(landing_type)))
 }
 

src/fighter/state/air_attack.rs

@@ -93,7 +93,7 @@ impl FighterStateImpl for AirAttackState {
         let coll_interrupt = air::collision_interrupt(
             state_context,
             crate::fighter::state::land::LandingType::Normal,
-            false,
+            Default::default(),
         );
 
         coll_interrupt.map(|state| {

src/fighter/state/air_dodge.rs

@@ -1,17 +1,9 @@
 use crate::{
     fighter::{
-        FighterInvulnerabilityState,
+        FighterInvulnerabilityState, animation::AnimKind, state::{
-        animation::AnimKind,
+            CollisionContext, EnterContext, FighterState, FighterStateImpl, InterruptContext, UpdateContext, air::{self, AirborneStateCommon}, fall::FallState, land::{LandingState, LandingType},
-        state::{
-            CollisionContext, EnterContext, FighterState, FighterStateImpl, InterruptContext,
-            UpdateContext,
-            air::{self, AirborneStateCommon},
-            fall::FallState,
-            land::LandingType,
         },
-    },
+    }, input, math::vec::FGVec2, stage::line::{StageLineID, StagePolyLineSegmentType},
-    input,
-    math::vec::FGVec2,
 };
 
 #[derive(Debug, Clone, Hash)]
@@ -41,18 +33,44 @@ impl FighterStateImpl for AirDodgeState {
         }
         state_context.velocity.0 *= state_context.fighter_attributes.air_dodge_decay;
 
-        air::apply_air_motion(
+        air::apply_air_motion_with_knockback(state_context);
-            state_context.velocity,
-            state_context.translation,
-            state_context.prev_translation,
-        );
     }
 
     fn check_collision_interrupt(
         &mut self,
         state_context: &mut CollisionContext,
     ) -> Option<FighterState> {
-        air::collision_interrupt(state_context, LandingType::Special, false)
+        let can_wavesnap = self.direction.y.is_zero() || self.direction.y.is_negative();
+        
+        if can_wavesnap {
+            for (poly_idx, poly) in state_context.stage_collision.stage_polys.iter().enumerate() {
+                for (segment_idx, segment) in poly.segments.iter().enumerate() {
+                    if !matches!(segment.segment_type, StagePolyLineSegmentType::Floor) {
+                        continue;
+                    }
+                    let bottom_point = state_context.translation.0 + state_context.ecb.get_bottom_point();
+                    let point_in_segment = segment.segment.closest_point(bottom_point);
+                    let dist_to_segment = point_in_segment.distance(bottom_point);
+                    if dist_to_segment <= state_context.waveland_snap_distance {
+                        state_context.ecb.bottom = point_in_segment - state_context.translation.0;
+                        state_context.ecb.rebase_onto_bottom();
+                        state_context.surface.land(StageLineID { polygon: poly_idx, segment: segment_idx }, state_context.ledge_info);
+                        state_context.knockback_velocity.0 = FGVec2::ZERO;
+                        state_context.knockback_state.clear();
+                        return Some(FighterState::Land(LandingState::create(LandingType::Special)));
+                    }
+                }
+            }
+        }
+
+        air::collision_interrupt(
+            state_context,
+            LandingType::Special,
+            crate::fighter::collision::AirCollisionOptions {
+                land_on_soft_platforms_from_below: true,
+                ..Default::default()
+            },
+        )
     }
 
     fn on_enter(&mut self, state_context: &mut EnterContext) {

src/fighter/state/angel.rs

@@ -43,8 +43,9 @@ impl FighterStateImpl for AngelState {
     
     fn check_collision_interrupt(
         &mut self,
-        _state_context: &mut super::CollisionContext,
+        state_context: &mut super::CollisionContext,
     ) -> Option<super::FighterState> {
+        state_context.apply_desired_ecb();
         None
     }
     

src/fighter/state/fall.rs

@@ -25,6 +25,7 @@ impl FighterStateImpl for FallState {
 
     fn on_enter(&mut self, state_context: &mut EnterContext) {
         state_context.play_animation(AnimKind::Fall, true);
+        state_context.velocity.x = state_context.velocity.x.clamp(-state_context.fighter_attributes.air_drift_max, state_context.fighter_attributes.air_drift_max);
     }
 
     fn update(&mut self, state_context: &mut UpdateContext) {
@@ -38,7 +39,10 @@ impl FighterStateImpl for FallState {
         air::collision_interrupt(
             state_context,
             crate::fighter::state::land::LandingType::Normal,
-            true,
+            crate::fighter::collision::AirCollisionOptions {
+                can_pass_through_soft_platforms: true,
+                ..Default::default()
+            },
         )
     }
     

src/fighter/state/ground.rs

@@ -2,16 +2,20 @@
 //! ECS types so it stays cheap to reason about and to unit-test — it has to be
 //! bit-for-bit deterministic for rollback.
 
+use crate::fighter::state::air_dodge::AirDodgeState;
 use crate::fighter::state::{
-    CollisionContext, FighterState, InterruptContext, air, crouch, dash, fall, ground_attack, turn, wait, walk,
+    CollisionContext, FighterState, InterruptContext, air, crouch, dash, fall, ground_attack, turn,
-};
+    wait, walk,
-use crate::fighter::{
-    FighterAttributes, FighterTranslation, FighterVelocity,
 };
+use crate::fighter::{collision, ecb};
+use crate::fighter::{FighterAttributes, FighterTranslation, FighterVelocity};
 use crate::game_settings::GameSettings;
+use crate::input::FighterInput;
 use crate::math::int::{FGWide, FGi32};
 use crate::math::vec::FGVec2;
-use crate::stage::line::{StageLineID, StagePoly, StagePolyLineSegment, StagePolyLineSegmentType};
+use crate::stage::line::{StagePoly, StagePolyLineSegment, StagePolyLineSegmentType};
+#[cfg(test)]
+use crate::stage::line::StageLineID;
 
 pub fn apply_grounded_friction(friction: FGi32, ground_vel: FGi32) -> FGi32 {
     if friction.abs() > ground_vel.abs() {
@@ -146,10 +150,7 @@ fn resolve_grounded_position(
     GroundedPositionResult::InAir
 }
 
-pub fn apply_grounded_motion(
+pub fn apply_grounded_motion(velocity: &FighterVelocity, translation: &mut FighterTranslation) {
-    velocity: &FighterVelocity,
-    translation: &mut FighterTranslation,
-) {
     // Vertical velocity should be 0 on the ground
     translation.0 += FGVec2::new(velocity.0.x, FGi32::ZERO);
 }
@@ -174,61 +175,77 @@ pub fn collide_with_stage_grounded(
     state_context: &mut CollisionContext,
     can_walk_off: bool,
 ) -> GroundedMotionResult {
-    let translation = &mut state_context.translation;
+    let Some(mut line_id) = state_context.surface.line_id() else {
-    let ecb = &state_context.ecb;
+        state_context.apply_desired_ecb();
-    let stage_collision = state_context.stage_collision;
-
-    let Some(current_line_id) = state_context.surface.line_id() else {
         return GroundedMotionResult::InAir;
     };
+    let requested_translation = state_context.translation.0;
+    let movement = requested_translation - state_context.prev_translation.0;
+    let largest_change = movement
+        .x
+        .abs()
+        .max(movement.y.abs())
+        .max(ecb::ecb_max_delta(state_context.ecb, state_context.desired_ecb));
+    let steps = collision::collision_step_count(largest_change);
+    let movement_per_step = movement / FGi32::from_num(steps);
+    let mut current_position = state_context.prev_translation.0;
+    let mut current_ecb = *state_context.ecb;
 
-    let stage_poly = stage_collision.stage_polys.get(current_line_id.polygon);
+    for step in 0..steps {
+        ecb::interpolate_ecb(
+            &mut current_ecb,
+            *state_context.desired_ecb,
+            FGi32::ONE / FGi32::from_num(steps - step),
+        );
+        current_position = if step + 1 == steps {
+            requested_translation
+        } else {
+            state_context.prev_translation.0
+                + movement_per_step * FGi32::from_num(step + 1)
+        };
 
-    if let Some(stage_poly) = stage_poly {
+        let Some(stage_poly) = state_context.stage_collision.stage_polys.get(line_id.polygon) else {
-        let ecb_bottom_pos = translation.0 + ecb.get_bottom_point();
+            *state_context.ecb = current_ecb;
+            state_context.translation.0 = current_position;
+            state_context.surface.apply_airborne_policy(
+                crate::fighter::surface::EcbLockPolicy::StartOnDetach,
+                state_context.leave_ground_ecb_lock_duration,
+            );
+            return GroundedMotionResult::InAir;
+        };
         match resolve_grounded_position(
             stage_poly,
-            current_line_id.segment,
+            line_id.segment,
-            ecb_bottom_pos,
+            current_position + current_ecb.bottom,
             can_walk_off,
         ) {
-            GroundedPositionResult::InGround {
+            GroundedPositionResult::InGround { point, segment_idx, blocked } => {
-                point,
+                line_id.segment = segment_idx;
-                segment_idx,
+                current_position = point - current_ecb.bottom;
-                blocked,
+                let segment = stage_poly.get_segment(segment_idx).unwrap();
-            } => {
-                let current_segment = stage_poly.get_segment(segment_idx).unwrap();
-                translation.0 = point - ecb.get_bottom_point();
                 state_context.velocity.0 = if blocked {
                     FGVec2::ZERO
                 } else {
                     state_context.velocity.0
-                        - state_context
+                        - state_context.velocity.0.project_onto_normalized(segment.normal)
-                            .velocity
-                            .0
-                            .project_onto_normalized(current_segment.normal)
                 };
-                state_context.surface.land(StageLineID {
-                    polygon: current_line_id.polygon,
-                    segment: segment_idx,
-                });
-                GroundedMotionResult::InGround
             }
             GroundedPositionResult::InAir => {
+                *state_context.ecb = current_ecb;
+                state_context.translation.0 = current_position;
                 state_context.surface.apply_airborne_policy(
                     crate::fighter::surface::EcbLockPolicy::StartOnDetach,
                     state_context.leave_ground_ecb_lock_duration,
                 );
-                GroundedMotionResult::InAir
+                return GroundedMotionResult::InAir;
             }
         }
-    } else {
-        state_context.surface.apply_airborne_policy(
-            crate::fighter::surface::EcbLockPolicy::StartOnDetach,
-            state_context.leave_ground_ecb_lock_duration,
-        );
-        GroundedMotionResult::InAir
     }
+
+    *state_context.ecb = current_ecb;
+    state_context.translation.0 = current_position;
+    state_context.surface.land(line_id, state_context.ledge_info);
+    GroundedMotionResult::InGround
 }
 
 pub fn collision_interrupt(ctx: &mut CollisionContext, can_walk_off: bool) -> Option<FighterState> {
@@ -243,10 +260,14 @@ pub fn collision_interrupt(ctx: &mut CollisionContext, can_walk_off: bool) -> Op
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::fighter::ecb::FighterPreviousECB;
+    use crate::fighter::attack::{FighterKnockbackState, FighterKnockbackVelocity};
-    use crate::fighter::{FighterECB, FighterPreviousTranslation, FighterSurfaceState};
+    use crate::fighter::ecb::{FighterDesiredECB, FighterPreviousECB};
-    use crate::stage::line::StagePolyType;
+    use crate::fighter::{
+        FighterECB, FighterLedgeInformation, FighterPreviousTranslation, FighterSurfaceState,
+    };
     use crate::input::FighterInput;
+    use crate::math::rect::FGRect;
+    use crate::stage::line::StagePolyType;
 
     fn two_segment_floor() -> StagePoly {
         StagePoly::build(
@@ -357,6 +378,7 @@ mod tests {
     fn grounded_collision_updates_surface_segment() {
         let stage_collision = crate::stage::line::StageCollision {
             stage_polys: vec![two_segment_floor()],
+            ..crate::stage::line::StageCollision::default()
         };
         let mut surface = FighterSurfaceState::Grounded {
             line_id: StageLineID {
@@ -367,6 +389,9 @@ mod tests {
         let mut translation = FighterTranslation(FGVec2::lit("11", "0"));
         let previous_translation = FighterPreviousTranslation(translation.0);
         let mut velocity = FighterVelocity::default();
+        let mut knockback_velocity = FighterKnockbackVelocity::default();
+        let mut knockback_state = FighterKnockbackState::default();
+        let mut ledge_info = FighterLedgeInformation::default();
         let mut ecb = FighterECB {
             bottom: FGVec2::lit("0.0", "-0.5"),
             top: FGVec2::lit("0.0", "0.5"),
@@ -374,19 +399,29 @@ mod tests {
             right: FGVec2::lit("0.5", "0.0"),
         };
         let previous_ecb = FighterPreviousECB::from(ecb);
+        let mut desired_ecb = FighterDesiredECB::from(ecb);
         let mut presentation_snap = crate::fighter::FighterPresentationSnap::default();
         let mut context = CollisionContext {
             translation: &mut translation,
             prev_translation: &previous_translation,
             input: &FighterInput::default(),
             velocity: &mut velocity,
+            knockback_velocity: &mut knockback_velocity,
+            knockback_state: &mut knockback_state,
             surface: &mut surface,
             ecb: &mut ecb,
+            desired_ecb: &mut desired_ecb,
+            ledge_info: &mut ledge_info,
             prev_ecb: &previous_ecb,
             stage_collision: &stage_collision,
             leave_ground_ecb_lock_duration: 10,
             presentation_snap: &mut presentation_snap,
             downward_stick_threshold: FGi32::ONE,
+            fighter_ledge_collision_box: FGRect {
+                origin: FGVec2::ZERO,
+                end: FGVec2::ZERO,
+            },
+            waveland_snap_distance: FGi32::ZERO,
         };
 
         assert!(matches!(
@@ -412,6 +447,7 @@ mod tests {
                     (FGVec2::lit("10", "0"), StagePolyLineSegmentType::Floor),
                 ],
             )],
+            ..crate::stage::line::StageCollision::default()
         };
         let mut surface = FighterSurfaceState::Grounded {
             line_id: StageLineID {
@@ -422,6 +458,8 @@ mod tests {
         let mut translation = FighterTranslation(FGVec2::lit("11", "0"));
         let previous_translation = FighterPreviousTranslation(translation.0);
         let mut velocity = FighterVelocity::default();
+        let mut knockback_velocity = FighterKnockbackVelocity::default();
+        let mut knockback_state = FighterKnockbackState::default();
         let mut ecb = FighterECB {
             bottom: FGVec2::lit("0.0", "-0.5"),
             top: FGVec2::lit("0.0", "0.5"),
@@ -429,19 +467,30 @@ mod tests {
             right: FGVec2::lit("0.5", "0.0"),
         };
         let previous_ecb = FighterPreviousECB::from(ecb);
+        let mut desired_ecb = FighterDesiredECB::from(ecb);
         let mut presentation_snap = crate::fighter::FighterPresentationSnap::default();
+        let mut ledge_info = FighterLedgeInformation::default();
         let mut context = CollisionContext {
             translation: &mut translation,
             prev_translation: &previous_translation,
             input: &FighterInput::default(),
             velocity: &mut velocity,
+            knockback_velocity: &mut knockback_velocity,
+            knockback_state: &mut knockback_state,
             surface: &mut surface,
             ecb: &mut ecb,
+            desired_ecb: &mut desired_ecb,
+            ledge_info: &mut ledge_info,
             prev_ecb: &previous_ecb,
             stage_collision: &stage_collision,
             leave_ground_ecb_lock_duration: 10,
             presentation_snap: &mut presentation_snap,
             downward_stick_threshold: FGi32::ONE,
+            fighter_ledge_collision_box: FGRect {
+                origin: FGVec2::ZERO,
+                end: FGVec2::ZERO,
+            },
+            waveland_snap_distance: FGi32::ZERO,
         };
 
         assert!(matches!(
@@ -477,3 +526,22 @@ pub fn grounded_movement_standstill_common_interrupts(
         None
     }
 }
+
+pub fn perform_wavedash(input: &FighterInput, game_settings: &GameSettings) -> FighterState {
+    // If aiming sideways and in the deadzone, do a perfect wavedash
+    // TODO: Improve this so we don't have to go through the airborne state first
+    let mut wavedash_dir = input.get_last_frame().movement.normalize_or_zero();
+    let movement = input.get_last_frame().movement;
+    if movement.y.is_zero() && !movement.x.is_zero() {
+        wavedash_dir.y = -game_settings.input_common.stick_deadzone - FGi32::lit("-0.01");
+        wavedash_dir.x = movement.x.signum();
+    }
+
+    if wavedash_dir == FGVec2::ZERO {
+        wavedash_dir = FGVec2::lit("0.0", "-1.0");
+    }
+
+    FighterState::AirDodge(AirDodgeState {
+        direction: wavedash_dir.normalize_or_zero(),
+    })
+}

src/fighter/state/hitstun.rs

@@ -1,8 +1,6 @@
 use crate::{
     fighter::{
-        animation::AnimKind,
+        animation::AnimKind, attack::{self, FighterHitReaction}, state::{
-        attack::{self, FighterHitReaction},
-        state::{
             CollisionContext, EnterContext, ExitContext, FighterState, FighterStateImpl,
             InterruptContext, UpdateContext,
             air::{self, AirborneStateCommon},
@@ -11,7 +9,7 @@ use crate::{
             land::LandingType,
             wait::WaitState,
         },
-    }, math::{int::FGi32, vec::FGVec2},
+    }, math::vec::FGVec2,
 };
 
 #[derive(Clone, Debug, Hash)]
@@ -25,14 +23,20 @@ pub struct HitstunState {
     pub hit_reaction: FighterHitReaction,
     pub hitstop_kind: HitstopStateKind,
     knockback_applied: bool,
+    stack_previous_knockback: bool,
 }
 
 impl HitstunState {
-    pub fn new(hit_reaction: FighterHitReaction, hitstop_kind: HitstopStateKind) -> Self {
+    pub fn new(
+        hit_reaction: FighterHitReaction,
+        hitstop_kind: HitstopStateKind,
+        stack_previous_knockback: bool,
+    ) -> Self {
         Self {
             hit_reaction,
             hitstop_kind,
             knockback_applied: false,
+            stack_previous_knockback,
         }
     }
 }
@@ -40,6 +44,35 @@ impl HitstunState {
 impl FighterStateImpl for HitstunState {
     const NAME: &'static str = "Hitstun";
 
+    fn check_interrupt(&self, state_context: &mut InterruptContext) -> Option<FighterState> {
+        if state_context.get_current_animation_frame() > self.hit_reaction.hitstun_frames {
+            match &self.hitstop_kind {
+                HitstopStateKind::Grounded => Some(FighterState::Wait(WaitState)),
+                HitstopStateKind::Airborne => Some(FighterState::Fall(FallState::new(
+                    AirborneStateCommon::default(),
+                ))),
+            }
+        } else {
+            None
+        }
+    }
+
+    fn on_enter(&mut self, state_context: &mut EnterContext) {
+        let animation = match self.hitstop_kind {
+            HitstopStateKind::Grounded => AnimKind::FlinchGround,
+            HitstopStateKind::Airborne => AnimKind::FlinchAir,
+        };
+        state_context.play_animation(animation, false);
+        state_context.velocity.0 = FGVec2::ZERO;
+    }
+
+    fn on_exit(&mut self, state_context: &mut ExitContext) {
+        if matches!(self.hitstop_kind, HitstopStateKind::Grounded) {
+            state_context.knockback_velocity.0 = FGVec2::ZERO;
+            state_context.knockback_state.clear();
+        }
+    }
+
     fn name(&self) -> String {
         let hitstop_kind = match self.hitstop_kind {
             HitstopStateKind::Grounded => "Grounded",
@@ -54,28 +87,29 @@ impl FighterStateImpl for HitstunState {
         format!("Hitstun ({hitstop_kind}, {hit_reaction_type})")
     }
 
-    fn check_interrupt(&self, state_context: &mut InterruptContext) -> Option<FighterState> {
-        if state_context.get_current_animation_frame() > self.hit_reaction.hitstun_frames {
-            match &self.hitstop_kind {
-                HitstopStateKind::Grounded => Some(FighterState::Wait(WaitState)),
-                HitstopStateKind::Airborne => Some(FighterState::Fall(FallState::new(
-                    AirborneStateCommon::default(),
-                ))),
-            }
-        } else {
-            None
-        }
-    }
-
     fn update(&mut self, ctx: &mut UpdateContext) {
         if !self.knockback_applied {
-            let launch_direction = attack::directional_influence::apply_directional_influence(
+            let new_launch_direction = attack::directional_influence::apply_directional_influence(
-                ctx.input.get_last_frame().movement,
+                FGVec2::ZERO,
                 self.hit_reaction.launch_angle,
                 ctx.game_settings.fighter_common.di_max_angle,
             );
+            let new_knockback = new_launch_direction * self.hit_reaction.launch_velocity;
+            let combined_knockback = if self.stack_previous_knockback {
+                attack::stack_knockback(ctx.knockback_velocity.0, new_knockback)
+            } else {
+                new_knockback
+            };
+            let launch_speed = combined_knockback.length();
+            let launch_direction =
+                attack::directional_influence::apply_directional_influence_to_direction(
+                    ctx.input.get_last_frame().movement,
+                    combined_knockback.normalize_or_zero(),
+                    ctx.game_settings.fighter_common.di_max_angle,
+                );
 
-            ctx.knockback_velocity.0 = launch_direction * self.hit_reaction.launch_velocity;
+            ctx.knockback_velocity.0 = launch_direction * launch_speed;
+            ctx.knockback_state.restart();
             self.knockback_applied = true;
         }
 
@@ -83,30 +117,19 @@ impl FighterStateImpl for HitstunState {
             HitstopStateKind::Grounded => {}
             HitstopStateKind::Airborne => {
                 air::integrate_gravity(ctx.velocity, ctx.fighter_attributes, false);
+                air::apply_air_motion_with_knockback(ctx);
             }
         }
 
-        let speed = ctx.knockback_velocity.length();
+        if matches!(self.hitstop_kind, HitstopStateKind::Grounded) {
-        let next_speed = speed
+            attack::decay_knockback(
-            .saturating_sub(ctx.game_settings.fighter_common.knockback_decay_per_frame)
+                ctx.knockback_velocity,
-            .max(FGi32::ZERO);
+                ctx.knockback_state,
-
+                ctx.game_settings.fighter_common.knockback_decay_per_frame,
-        ctx.knockback_velocity.0 = ctx.knockback_velocity.normalize_or_zero() * next_speed;
+            );
-
+        }
-        ctx.translation.0 += ctx.velocity.0 + ctx.knockback_velocity.0;
     }
 
-    fn on_enter(&mut self, state_context: &mut EnterContext) {
-        let animation = match self.hitstop_kind {
-            HitstopStateKind::Grounded => AnimKind::FlinchGround,
-            HitstopStateKind::Airborne => AnimKind::FlinchAir,
-        };
-        state_context.play_animation(animation, false);
-        state_context.velocity.0 = FGVec2::ZERO;
-    }
-
-    fn on_exit(&mut self, _state_context: &mut ExitContext) {}
-
     fn check_collision_interrupt(
         &mut self,
         state_context: &mut CollisionContext,
@@ -114,7 +137,7 @@ impl FighterStateImpl for HitstunState {
         match &mut self.hitstop_kind {
             HitstopStateKind::Grounded => collision_interrupt(state_context, true),
             HitstopStateKind::Airborne => {
-                air::collision_interrupt(state_context, LandingType::Normal, false)
+                air::collision_interrupt(state_context, LandingType::Normal, Default::default())
             }
         }
     }

src/fighter/state/jump.rs

@@ -2,9 +2,9 @@
 use crate::{
     fighter::{
         animation::AnimKind, state::{
-            CollisionContext, EnterContext, FighterState, FighterStateImpl, InterruptContext, UpdateContext, air::{self, AirborneStateCommon}, air_dodge::AirDodgeState, ground, ground_attack,
+            CollisionContext, EnterContext, FighterState, FighterStateImpl, InterruptContext, UpdateContext, air::{self, AirborneStateCommon}, ground::{self}, ground_attack,
         },
-    }, input::{DigitalAction, FighterCommands}, math::{int::FGi32, vec::FGVec2},
+    }, input::{DigitalAction, FighterCommands},
 };
 #[derive(Debug, Hash, Clone, Copy)]
 pub enum JumpType {
@@ -50,27 +50,7 @@ impl FighterStateImpl for JumpSquatState {
         }
         // Special handling for wavedash from jump squat
         if state_context.input.has_command(FighterCommands::Shield) {
-            // If aiming sideways and in the deadzone, do a perfect wavedash
+            Some(ground::perform_wavedash(state_context.input, state_context.game_settings))
-            // TODO: Improve this so we don't have to go through the airborne state first
-            let mut wavedash_dir = state_context
-                .input
-                .get_last_frame()
-                .movement
-                .normalize_or_zero();
-            let movement = state_context.input.get_last_frame().movement;
-            if movement.y.is_zero() && !movement.x.is_zero() {
-                wavedash_dir.y =
-                    -state_context.game_settings.input_common.stick_deadzone - FGi32::lit("-0.01");
-                wavedash_dir.x = movement.x.signum();
-            }
-
-            if wavedash_dir == FGVec2::ZERO {
-                wavedash_dir = FGVec2::lit("0.0", "-1.0");
-            }
-
-            Some(FighterState::AirDodge(AirDodgeState {
-                direction: wavedash_dir.normalize_or_zero(),
-            }))
         } else if self.duration_counter >= state_context.fighter_attributes.jumpsquat_duration {
             let tap_jump_held = matches!(self.initiator, JumpStateInitiator::Tap)
                 && state_context.input.get_last_frame().movement.y
@@ -119,6 +99,8 @@ impl FighterStateImpl for JumpSquatState {
 
     fn on_exit(&mut self, state_context: &mut crate::fighter::state::ExitContext) {
         state_context.input.disable_hold_all();
+        // We clear tap jump here, it may have weird interactions with air dodging up
+        state_context.input.clear_command(FighterCommands::TapJump);
     }
 
     fn is_visually_grounded<'a>(&'a self) -> bool {
@@ -194,7 +176,10 @@ impl FighterStateImpl for JumpState {
         air::collision_interrupt(
             state_context,
             crate::fighter::state::land::LandingType::Normal,
-            true,
+            crate::fighter::collision::AirCollisionOptions {
+                can_pass_through_soft_platforms: true,
+                ..Default::default()
+            },
         )
     }
 

src/fighter/state/ledge_action.rs

@@ -0,0 +1,157 @@
+use super::{CollisionContext, EnterContext, FighterStateImpl, InterruptContext, UpdateContext};
+use crate::fighter::animation::AnimKind;
+use crate::fighter::state::air::AirborneStateCommon;
+use crate::fighter::state::jump::{JumpState, JumpStateInitiator, JumpType};
+use crate::fighter::state::wait::WaitState;
+use crate::fighter::state::{FighterState, ground};
+use crate::fighter::FighterFacingDirection;
+use crate::input::FighterCommands;
+use crate::math::int::FGi32;
+use crate::math::vec::FGVec2;
+use crate::stage::line::{StageLedgeSide, StageVertexID};
+
+#[derive(Debug, Clone, Hash)]
+pub enum LedgeAction {
+    Jump(JumpStateInitiator),
+    GetUp
+}
+
+#[derive(Debug, Clone, Hash)]
+pub struct LedgeActionState {
+    pub ledge_id: StageVertexID,
+    pub ledge_action: LedgeAction,
+    pub is_in_grounded_phase: bool,
+}
+
+impl LedgeActionState {
+    pub fn create_jump(ledge_id: StageVertexID, initiator: JumpStateInitiator) -> Self {
+        LedgeActionState {
+            ledge_id,
+            ledge_action: LedgeAction::Jump(initiator),
+            is_in_grounded_phase: false,
+        }
+    }
+    pub fn create_getup(ledge_id: StageVertexID) -> Self {
+        LedgeActionState {
+            ledge_id,
+            ledge_action: LedgeAction::GetUp,
+            is_in_grounded_phase: false,
+        }
+    }
+}
+
+impl FighterStateImpl for LedgeActionState {
+    const NAME: &'static str = "LedgeAction";
+    fn check_interrupt(&self, state_context: &mut InterruptContext) -> Option<FighterState> {
+        match &self.ledge_action {
+            LedgeAction::Jump(initiator) => {
+                if state_context.is_current_animation_finished() {
+                    if state_context.input.has_command(FighterCommands::Shield) {
+                        Some(ground::perform_wavedash(state_context.input, state_context.game_settings))
+                    } else {
+                        Some(FighterState::Jump(JumpState {
+                            jump_type: JumpType::DoubleJump,
+                            airborne_state_common: AirborneStateCommon::default(),
+                            initiator: initiator.clone()
+                        }))
+                    }
+                } else {
+                    None
+                }
+            },
+            LedgeAction::GetUp => {
+                if state_context.is_current_animation_finished() {
+                    Some(FighterState::Wait(WaitState))
+                } else {
+                    None
+                }
+            },
+        }
+    }
+
+    fn on_enter(&mut self, state_context: &mut EnterContext) {
+        match self.ledge_action {
+            LedgeAction::Jump(_) => {
+                state_context.play_animation(AnimKind::LedgeJump, false);
+                state_context.input.enable_hold_all(10);
+                state_context.input.clear_command(FighterCommands::Jump);
+                state_context.input.clear_command(FighterCommands::TapJump);
+            },
+            LedgeAction::GetUp => {
+                state_context.play_animation(AnimKind::LedgeGetUp, false);
+            },
+        }
+
+        state_context.velocity.0 = FGVec2::ZERO;
+        state_context.knockback_velocity.0 = FGVec2::ZERO;
+        state_context.knockback_state.clear();
+        let Some(ledge) = state_context.stage_collision.find_ledge_by_vertex(self.ledge_id) else {
+            return;
+        };
+        state_context.translation.0 = ledge.position;
+        *state_context.facing_direction = match ledge.hang_side {
+            StageLedgeSide::Left => FighterFacingDirection::Right,
+            StageLedgeSide::Right => FighterFacingDirection::Left,
+        };
+        if let Some(root_position) = state_context.initial_animation_root_position() {
+            state_context.translation.0 = root_position;
+        }
+        state_context.presentation_snap.0 = true;
+    }
+
+    fn update(&mut self, state_context: &mut UpdateContext) {
+        if !self.is_in_grounded_phase {
+            let root_pos = state_context.animation_root_position.unwrap_or_default();
+            let Some(ledge) = state_context.stage_collision.find_ledge_by_vertex(self.ledge_id) else {
+                return;
+            };
+
+            let ledge_pos = ledge.position;
+            let ledge_modifier = match ledge.hang_side {
+                StageLedgeSide::Left => FGi32::ONE,
+                StageLedgeSide::Right => FGi32::NEG_ONE,
+            };
+
+            let normalized_root_position = root_pos - ledge_pos;
+            let normalized_root_position = FGVec2::new(normalized_root_position.x * ledge_modifier, normalized_root_position.y);
+            
+            if normalized_root_position.x.is_positive() && normalized_root_position.y.is_positive() {
+                let Some((segment_id, _)) = state_context
+                    .stage_collision
+                    .find_ledge_ground_segment(self.ledge_id)
+                else {
+                    return;
+                };
+
+                self.is_in_grounded_phase = true;
+                state_context.translation.0 = ledge.position;
+                state_context.surface.land(segment_id, state_context.ledge_info);
+            }
+        }
+
+        if self.is_in_grounded_phase {
+            state_context.velocity.0.x = state_context.animation_root_motion_delta.x;
+            ground::apply_grounded_motion(
+                state_context.velocity,
+                state_context.translation,
+            );
+        } else {
+            if let Some(root_position) = state_context.animation_root_position {
+                state_context.translation.0 = root_position;
+            }
+        }
+
+    }
+
+    fn check_collision_interrupt(
+        &mut self,
+        state_context: &mut CollisionContext,
+    ) -> Option<FighterState> {
+        state_context.apply_desired_ecb();
+        None
+    }
+
+    fn is_visually_grounded<'a>(&'a self) -> bool {
+        self.is_in_grounded_phase
+    }
+}

src/fighter/state/ledge_grab.rs

@@ -0,0 +1,75 @@
+use super::{
+    EnterContext, FighterStateImpl, InterruptContext, UpdateContext,
+};
+use crate::fighter::{FighterFacingDirection, FighterInvulnerabilityState};
+use crate::fighter::animation::AnimKind;
+use crate::fighter::state::{ExitContext, FighterState};
+use crate::fighter::state::air::AirborneStateCommon;
+use crate::fighter::state::ledge_wait::LedgeWaitState;
+use crate::stage::line::{StageLedgeSide, StageVertexID};
+
+#[derive(Debug, Clone, Hash)]
+pub struct LedgeGrabState {
+    ledge_id: StageVertexID
+}
+
+impl LedgeGrabState {
+    pub fn new(ledge_id: StageVertexID) -> Self {
+        Self {
+            ledge_id
+        }
+    }
+}
+
+impl FighterStateImpl for LedgeGrabState {
+    const NAME: &'static str = "LedgeGrab";
+    fn check_interrupt(&self, state_context: &mut InterruptContext) -> Option<FighterState> {
+        if state_context.is_current_animation_finished() {
+            Some(FighterState::LedgeWait(LedgeWaitState {
+                airborne_state_common: AirborneStateCommon::default(),
+                ledge_id: self.ledge_id.clone()
+            }))
+        } else {
+            None
+        }
+    }
+
+    fn on_enter(&mut self, state_context: &mut EnterContext) {
+        state_context.play_animation(AnimKind::LedgeGrab, false);
+        state_context.knockback_velocity.0 = crate::math::vec::FGVec2::ZERO;
+        state_context.knockback_state.clear();
+
+        *state_context.vulnerability = FighterInvulnerabilityState::Intangible {
+            frames_remaining: None,
+        };
+
+        let Some(ledge) = state_context.stage_collision.find_ledge_by_vertex(self.ledge_id) else {
+            return;
+        };
+        state_context.translation.0 = ledge.position;
+        *state_context.facing_direction = match ledge.hang_side {
+            StageLedgeSide::Left => FighterFacingDirection::Right,
+            StageLedgeSide::Right => FighterFacingDirection::Left,
+        };
+        if let Some(root_position) = state_context.initial_animation_root_position() {
+            state_context.translation.0 = root_position;
+        }
+        state_context.presentation_snap.0 = true;
+
+
+    }
+
+    fn on_exit(&mut self, state_context: &mut ExitContext) {
+        *state_context.vulnerability = FighterInvulnerabilityState::Vulnerable;
+    }
+
+    fn is_visually_grounded<'a>(&'a self) -> bool {
+        false
+    }
+    
+    fn update(&mut self, state_context: &mut UpdateContext) {
+        if let Some(root_position) = state_context.animation_root_position {
+            state_context.translation.0 = root_position;
+        }
+    }
+}

src/fighter/state/ledge_wait.rs

@@ -0,0 +1,167 @@
+use super::{CollisionContext, EnterContext, FighterStateImpl, InterruptContext, UpdateContext};
+use crate::fighter::animation::AnimKind;
+use crate::fighter::state::air::AirborneStateCommon;
+use crate::fighter::state::fall::FallState;
+use crate::fighter::state::FighterState;
+use crate::fighter::state::jump::JumpStateInitiator;
+use crate::fighter::state::ledge_action::{LedgeActionState};
+use crate::fighter::{FighterFacingDirection, FighterInvulnerabilityState};
+use crate::input::FighterCommands;
+use crate::math::vec::FGVec2;
+use crate::stage::line::{StageLedgeSide, StageVertexID};
+
+#[derive(Debug, Clone, Hash)]
+pub struct LedgeWaitState {
+    pub airborne_state_common: AirborneStateCommon,
+    pub ledge_id: StageVertexID,
+}
+
+impl FighterStateImpl for LedgeWaitState {
+    const NAME: &'static str = "LedgeWait";
+    fn check_interrupt(&self, state_context: &mut InterruptContext) -> Option<FighterState> {
+        if state_context.input.has_command(FighterCommands::Jump) {
+            return Some(FighterState::LedgeAction(LedgeActionState::create_jump(self.ledge_id, JumpStateInitiator::Button)));
+        } else if state_context.input.has_command(FighterCommands::TapJump) {
+            return Some(FighterState::LedgeAction(LedgeActionState::create_jump(self.ledge_id, JumpStateInitiator::Tap)));
+        }
+
+        if is_ledge_getup_input(state_context.input.get_last_frame().movement.x,
+            state_context.game_settings.input_common.run_stick_threshold,
+            state_context.facing_direction) {
+                return Some(FighterState::LedgeAction(LedgeActionState::create_getup(self.ledge_id)));
+        }
+
+        if is_ledge_drop_input(state_context.input.get_last_frame().movement.x,
+            state_context.game_settings.input_common.run_stick_threshold,
+            state_context.facing_direction) {
+            state_context.ledge_grab_lockout.start(
+                state_context
+                    .game_settings
+                    .fighter_common
+                    .ledge_drop_regrab_lockout_duration_frames,
+            );
+            return Some(FighterState::Fall(FallState::new(
+                AirborneStateCommon { is_fast_falling: false },
+            )));
+        }
+        if is_ledge_drop_fastfall_input(
+            state_context.input.get_last_frame().movement.y,
+            state_context.game_settings.input_common.run_stick_threshold,
+        ) {
+            state_context.ledge_grab_lockout.start(
+                state_context
+                    .game_settings
+                    .fighter_common
+                    .ledge_drop_regrab_lockout_duration_frames,
+            );
+            return Some(FighterState::Fall(FallState::new(
+                AirborneStateCommon { is_fast_falling: true },
+            )));
+        }
+
+        None
+    }
+
+    fn on_enter(&mut self, state_context: &mut EnterContext) {
+        state_context.velocity.0 = FGVec2::ZERO;
+        state_context.knockback_velocity.0 = FGVec2::ZERO;
+        state_context.knockback_state.clear();
+        
+        if state_context.ledge_info.grab_count < state_context.game_settings.fighter_common.max_ledge_grab_count {
+            *state_context.vulnerability = FighterInvulnerabilityState::Intangible {
+                frames_remaining: Some(
+                    state_context
+                    .game_settings
+                    .fighter_common
+                    .ledge_grab_invulnerability_duration,
+                ),
+            };
+        }
+
+        state_context.ledge_info.grab_count = state_context.ledge_info.grab_count.saturating_add(1);
+        
+        let Some(ledge) = state_context.stage_collision.find_ledge_by_vertex(self.ledge_id) else {
+            return;
+        };
+        state_context.translation.0 = ledge.position;
+        *state_context.facing_direction = match ledge.hang_side {
+            StageLedgeSide::Left => FighterFacingDirection::Right,
+            StageLedgeSide::Right => FighterFacingDirection::Left,
+        };
+        state_context.play_animation(AnimKind::LedgeWait, true);
+        if let Some(root_position) = state_context.initial_animation_root_position() {
+            state_context.translation.0 = root_position;
+        }
+        state_context.presentation_snap.0 = true;
+    }
+
+    fn update(&mut self, state_context: &mut UpdateContext) {
+        if let Some(root_position) = state_context.animation_root_position {
+            state_context.translation.0 = root_position;
+        }
+    }
+
+    fn check_collision_interrupt(
+        &mut self,
+        state_context: &mut CollisionContext,
+    ) -> Option<FighterState> {
+        state_context.apply_desired_ecb();
+        None
+    }
+
+    fn is_visually_grounded<'a>(&'a self) -> bool {
+        false
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::math::int::FGi32;
+
+    #[test]
+    fn ledge_drop_uses_the_run_stick_threshold() {
+        let threshold = FGi32::lit("0.625");
+
+        assert!(is_ledge_drop_fastfall_input(FGi32::lit("-0.625"), threshold));
+        assert!(is_ledge_drop_fastfall_input(FGi32::lit("-1.0"), threshold));
+        assert!(!is_ledge_drop_fastfall_input(FGi32::lit("-0.624"), threshold));
+    }
+}
+
+fn is_ledge_drop_fastfall_input(
+    vertical_input: crate::math::int::FGi32,
+    threshold: crate::math::int::FGi32,
+) -> bool {
+    vertical_input <= -threshold
+}
+
+fn is_ledge_drop_input(
+    horizontal_input: crate::math::int::FGi32,
+    threshold: crate::math::int::FGi32,
+    facing_dir: &FighterFacingDirection,
+) -> bool {
+    let dir = facing_dir.to_sign();
+    if horizontal_input.abs() > threshold {
+        if dir != horizontal_input.signum() {
+            return true;
+        }
+    }
+
+    false
+}
+
+fn is_ledge_getup_input(
+    horizontal_input: crate::math::int::FGi32,
+    threshold: crate::math::int::FGi32,
+    facing_dir: &FighterFacingDirection,
+) -> bool {
+    let dir = facing_dir.to_sign();
+    if horizontal_input.abs() > threshold {
+        if dir == horizontal_input.signum() {
+            return true;
+        }
+    }
+
+    false
+}

src/fighter/state/mod.rs

@@ -7,12 +7,12 @@ use bevy::prelude::*;
 
 use crate::fighter::animation::{AnimKind, FighterAnimationFrame};
 use crate::fighter::attack::{
-    FighterAttackScriptAssets, FighterKnockbackVelocity, FighterPendingHitReaction,
+    FighterAttackScriptAssets, FighterKnockbackState, FighterKnockbackVelocity,
-    FighterStaleMoveQueue, HitStop,
+    FighterPendingHitReaction, FighterStaleMoveQueue, HitStop,
 };
 use crate::fighter::attributes::FighterAttributes;
 use crate::fighter::baked_animation::{BakedFighterAnimations, FighterBoneMatrices};
-use crate::fighter::ecb::FighterPreviousECB;
+use crate::fighter::ecb::{self, FighterDesiredECB, FighterPreviousECB};
 use crate::fighter::manifest::FighterManifest;
 use crate::fighter::state::hitstun::HitstunState;
 use crate::fighter::surface::EcbLockPolicy;
@@ -20,14 +20,16 @@ use crate::fighter::visual::FighterAnimations;
 use crate::fighter::{
     Fighter, FighterDamage, FighterECB, FighterFacingDirection, FighterHitboxes, FighterHitstop,
     FighterHitstopShake, FighterHitstopShakeKind, FighterHitstopShakeRole,
-    FighterInvulnerabilityState, FighterPendingRespawn, FighterPresentationSnap,
+    FighterInvulnerabilityState, FighterLedgeInformation, FighterPendingRespawn,
-    FighterPreviousTranslation, FighterSurfaceState, FighterTranslation, FighterVelocity,
+    FighterPresentationSnap, FighterPreviousTranslation, FighterSurfaceState, FighterTranslation,
+    FighterVelocity,
 };
 use crate::game_settings::GameSettings;
 use crate::input::FighterInput;
 use crate::match_loading::MatchConfig;
 use crate::match_runtime::MatchState;
 use crate::math::int::FGi32;
+use crate::math::rect::FGRect;
 use crate::math::vec::FGVec2;
 use crate::math::vec3::FGVec3;
 use crate::player::Player;
@@ -47,6 +49,9 @@ pub mod ground_attack;
 pub mod hitstun;
 pub mod jump;
 pub mod land;
+pub mod ledge_action;
+pub mod ledge_grab;
+pub mod ledge_wait;
 pub mod platform_pass;
 pub mod run;
 pub mod turn;
@@ -115,8 +120,9 @@ pub trait FighterStateImpl: Sized {
 
     fn check_collision_interrupt(
         &mut self,
-        _state_context: &mut CollisionContext,
+        state_context: &mut CollisionContext,
     ) -> Option<FighterState> {
+        state_context.apply_desired_ecb();
         None
     }
 
@@ -135,6 +141,7 @@ pub struct AnimationStatus {
 pub struct InterruptContext<'a> {
     pub input: &'a FighterInput,
     pub facing_direction: &'a mut FighterFacingDirection,
+    pub ledge_grab_lockout: &'a mut FighterLedgeInformation,
     pub game_settings: &'a GameSettings,
     pub fighter_attributes: &'a FighterAttributes,
     pub surface: &'a FighterSurfaceState,
@@ -158,26 +165,48 @@ pub struct EnterContext<'a> {
     pub input: &'a mut FighterInput,
     pub hitboxes: &'a mut FighterHitboxes,
     pub velocity: &'a mut FighterVelocity,
+    pub translation: &'a mut FighterTranslation,
     pub knockback_velocity: &'a mut FighterKnockbackVelocity,
+    pub knockback_state: &'a mut FighterKnockbackState,
     pub stale_move_queue: &'a mut FighterStaleMoveQueue,
     pub facing_direction: &'a mut FighterFacingDirection,
     pub animation_frame: &'a mut FighterAnimationFrame,
+    pub presentation_snap: &'a mut FighterPresentationSnap,
     pub surface: &'a mut FighterSurfaceState,
     pub vulnerability: &'a mut FighterInvulnerabilityState,
+    pub ledge_info: &'a mut FighterLedgeInformation,
     pub fighter_attributes: &'a FighterAttributes,
     pub attack_script_assets: &'a FighterAttackScriptAssets,
     pub game_settings: &'a GameSettings,
+    pub stage_collision: &'a StageCollision,
+    baked_animations: &'a BakedFighterAnimations,
+    model_scale: FGi32,
 }
 
 impl EnterContext<'_> {
     pub fn play_animation(&mut self, kind: AnimKind, repeat: bool) {
         self.animation_frame.reset(kind, repeat);
     }
+
+    /// World-space root position authored for frame zero of the animation most
+    /// recently selected with [`Self::play_animation`].
+    pub fn initial_animation_root_position(&self) -> Option<FGVec2> {
+        let position = self
+            .baked_animations
+            .initial_root_position(self.animation_frame.kind, self.model_scale)?;
+        Some(self.translation.0 + animation_position_to_gameplay(position, self.facing_direction))
+    }
+
+    pub fn get_animation_duration(&self, kind: AnimKind) -> Option<usize> {
+        self.baked_animations.get_animation_duration(kind)
+    }
 }
 
 pub struct ExitContext<'a> {
     pub input: &'a mut FighterInput,
     pub hitboxes: &'a mut FighterHitboxes,
+    pub knockback_velocity: &'a mut FighterKnockbackVelocity,
+    pub knockback_state: &'a mut FighterKnockbackState,
     pub surface: &'a mut FighterSurfaceState,
     pub vulnerability: &'a mut FighterInvulnerabilityState,
 }
@@ -190,23 +219,29 @@ pub struct UpdateContext<'a> {
     pub velocity: &'a mut FighterVelocity,
     pub surface: &'a mut FighterSurfaceState,
     pub knockback_velocity: &'a mut FighterKnockbackVelocity,
+    pub knockback_state: &'a mut FighterKnockbackState,
     pub vulnerability: &'a mut FighterInvulnerabilityState,
+    pub ledge_info: &'a mut FighterLedgeInformation,
     pub game_settings: &'a GameSettings,
     /// Root motion in the fighter's gameplay plane: X is world-right and Y is
     /// world-up. Animation +Z is forward and is mirrored by facing direction.
     pub animation_root_motion_delta: FGVec2,
+    /// Current world-space root position implied by this animation frame.
+    /// States opt into root motion by assigning this to [`FighterTranslation`].
+    pub animation_root_position: Option<FGVec2>,
     pub animation_frame: u32,
     pub fighter_attributes: &'a FighterAttributes,
     pub attack_scripts: &'a Assets<FighterAttackScript>,
     pub attack_script_assets: &'a FighterAttackScriptAssets,
     pub facing_direction: &'a FighterFacingDirection,
+    pub stage_collision: &'a StageCollision,
 }
 
-fn animation_root_motion_to_gameplay(
+fn animation_position_to_gameplay(
-    delta: FGVec3,
+    position: FGVec3,
     facing_direction: &FighterFacingDirection,
 ) -> FGVec2 {
-    FGVec2::new(delta.z * facing_direction.to_sign(), delta.y)
+    FGVec2::new(position.z * facing_direction.to_sign(), position.y)
 }
 
 impl UpdateContext<'_> {
@@ -220,31 +255,55 @@ pub struct CollisionContext<'a> {
     pub prev_translation: &'a FighterPreviousTranslation,
     pub input: &'a FighterInput,
     pub velocity: &'a mut FighterVelocity,
+    pub knockback_velocity: &'a mut FighterKnockbackVelocity,
+    pub knockback_state: &'a mut FighterKnockbackState,
     pub surface: &'a mut FighterSurfaceState,
     pub ecb: &'a mut FighterECB,
+    pub desired_ecb: &'a mut FighterDesiredECB,
     pub prev_ecb: &'a FighterPreviousECB,
     pub stage_collision: &'a StageCollision,
     pub leave_ground_ecb_lock_duration: u32,
     pub presentation_snap: &'a mut FighterPresentationSnap,
+    pub ledge_info: &'a mut FighterLedgeInformation,
+    pub fighter_ledge_collision_box: FGRect,
     pub downward_stick_threshold: FGi32,
+    pub waveland_snap_distance: FGi32,
 }
 
 impl CollisionContext<'_> {
+    /// Commit the target pose before resolving this frame. The collision
+    /// substep resolver can later replace this with fractional steps.
+    pub fn apply_desired_ecb(&mut self) {
+        ecb::interpolate_ecb(self.ecb, *self.desired_ecb, FGi32::ONE);
+    }
+
     pub fn air_collide_with_stage(
-        &self,
+        &mut self,
-        can_ignore_soft_platforms: bool,
+        mut options: crate::fighter::collision::AirCollisionOptions,
     ) -> Option<crate::fighter::collision::AirCollisionWithStageResult> {
         let ignored_polys = self.surface.ignored_polygon_ids();
-        let ignore_soft_platforms = can_ignore_soft_platforms
+        options.can_pass_through_soft_platforms = options.can_pass_through_soft_platforms
             && self.input.get_last_frame().movement.y <= -self.downward_stick_threshold;
-        crate::fighter::collision::air_collide_with_stage(
+        crate::fighter::collision::air_collide_with_stage_substepped(
             self.prev_translation,
             self.translation,
-            self.prev_ecb,
+            self.velocity,
             self.ecb,
+            self.desired_ecb,
             self.stage_collision,
             &ignored_polys,
-            ignore_soft_platforms,
+            options,
+        )
+    }
+    pub fn air_collide_with_ledges(
+        &self,
+    ) -> Option<crate::fighter::collision::AirCollisionWithLedgeResult> {
+        if self.ledge_info.is_regrab_lockout_active() {
+            return None;
+        }
+        crate::fighter::collision::air_collide_with_ledges(
+            &self.fighter_ledge_collision_box,
+            self.stage_collision,
         )
     }
 }
@@ -260,6 +319,9 @@ fighter_states! {
     JumpSquat => jump::JumpSquatState,
     Jump => jump::JumpState,
     Land => land::LandingState,
+    LedgeWait => ledge_wait::LedgeWaitState,
+    LedgeAction => ledge_action::LedgeActionState,
+    LedgeGrab => ledge_grab::LedgeGrabState,
     AirDodge => air_dodge::AirDodgeState,
     Turn => turn::TurnState,
     GroundAttack => ground_attack::GroundAttackState,
@@ -279,12 +341,15 @@ pub struct FighterFrameQuery {
     pub velocity: &'static mut FighterVelocity,
     pub surface: &'static mut FighterSurfaceState,
     pub knockback_velocity: &'static mut FighterKnockbackVelocity,
+    pub knockback_state: &'static mut FighterKnockbackState,
     pub stale_move_queue: &'static mut FighterStaleMoveQueue,
     pub ecb: &'static mut FighterECB,
+    pub desired_ecb: &'static mut FighterDesiredECB,
     pub prev_ecb: &'static FighterPreviousECB,
     pub facing_direction: &'static mut FighterFacingDirection,
     pub animation_frame: &'static mut FighterAnimationFrame,
     pub vulnerability: &'static mut FighterInvulnerabilityState,
+    pub ledge_information: &'static mut FighterLedgeInformation,
     pub fighter: &'static Fighter,
     pub bone_matrices: &'static FighterBoneMatrices,
 }
@@ -320,6 +385,7 @@ impl<'w, 's> FighterFrameQueryItem<'w, 's> {
         InterruptContext {
             input: &self.input,
             facing_direction: &mut self.facing_direction,
+            ledge_grab_lockout: &mut self.ledge_information,
             game_settings,
             fighter_attributes: attributes,
             animation,
@@ -335,20 +401,30 @@ impl<'w, 's> FighterFrameQueryItem<'w, 's> {
         attributes: &'a FighterAttributes,
         attack_script_assets: &'a FighterAttackScriptAssets,
         game_settings: &'a GameSettings,
+        stage_collision: &'a StageCollision,
+        baked_animations: &'a BakedFighterAnimations,
+        model_scale: FGi32,
     ) -> EnterContext<'a> {
         EnterContext {
             input: &mut self.input,
             hitboxes: &mut self.hitboxes,
             velocity: &mut self.velocity,
             knockback_velocity: &mut self.knockback_velocity,
+            knockback_state: &mut self.knockback_state,
+            translation: &mut self.translation,
             stale_move_queue: &mut self.stale_move_queue,
             facing_direction: &mut self.facing_direction,
             animation_frame: &mut self.animation_frame,
             surface: &mut self.surface,
             vulnerability: &mut self.vulnerability,
+            presentation_snap: &mut self.presentation_snap,
+            ledge_info: &mut self.ledge_information,
             fighter_attributes: attributes,
             attack_script_assets,
             game_settings,
+            stage_collision,
+            baked_animations,
+            model_scale,
         }
     }
 
@@ -356,6 +432,8 @@ impl<'w, 's> FighterFrameQueryItem<'w, 's> {
         ExitContext {
             input: &mut self.input,
             hitboxes: &mut self.hitboxes,
+            knockback_velocity: &mut self.knockback_velocity,
+            knockback_state: &mut self.knockback_state,
             surface: &mut self.surface,
             vulnerability: &mut self.vulnerability,
         }
@@ -367,7 +445,16 @@ impl<'w, 's> FighterFrameQueryItem<'w, 's> {
         attributes: &'a FighterAttributes,
         attack_scripts: &'a Assets<FighterAttackScript>,
         attack_script_assets: &'a FighterAttackScriptAssets,
+        stage_collision: &'a StageCollision,
     ) -> UpdateContext<'a> {
+        let animation_root_motion_delta = animation_position_to_gameplay(
+            self.bone_matrices.root_motion_delta(),
+            &self.facing_direction,
+        );
+        let animation_root_position = self
+            .bone_matrices
+            .root_motion_position()
+            .map(|_| self.translation.0 + animation_root_motion_delta);
         UpdateContext {
             translation: &mut self.translation,
             prev_translation: &mut self.prev_translation,
@@ -376,39 +463,51 @@ impl<'w, 's> FighterFrameQueryItem<'w, 's> {
             velocity: &mut self.velocity,
             surface: &mut self.surface,
             knockback_velocity: &mut self.knockback_velocity,
+            knockback_state: &mut self.knockback_state,
             game_settings,
-            animation_root_motion_delta: animation_root_motion_to_gameplay(
+            animation_root_motion_delta,
-                self.bone_matrices.root_motion_delta(),
+            animation_root_position,
-                &self.facing_direction,
-            ),
             animation_frame: self.animation_frame.frame,
             vulnerability: &mut self.vulnerability,
+            ledge_info: &mut self.ledge_information,
             fighter_attributes: attributes,
             attack_scripts,
             attack_script_assets,
             facing_direction: &self.facing_direction,
+            stage_collision: &stage_collision,
         }
     }
 
     fn collision_context<'a>(
         &'a mut self,
         stage_collision: &'a StageCollision,
+        fighter_manifest: &'a FighterManifest,
         game_settings: &'a GameSettings,
     ) -> CollisionContext<'a> {
+        let fighter_ledge_collision_box = FGRect {
+            origin: self.translation.0 + fighter_manifest.ledge_grab_box_start,
+            end: self.translation.0 + fighter_manifest.ledge_grab_box_end,
+        };
         CollisionContext {
             translation: &mut self.translation,
             prev_translation: &self.prev_translation,
             presentation_snap: &mut self.presentation_snap,
             input: &self.input,
             velocity: &mut self.velocity,
+            knockback_velocity: &mut self.knockback_velocity,
+            knockback_state: &mut self.knockback_state,
             surface: &mut self.surface,
             ecb: &mut self.ecb,
+            desired_ecb: &mut self.desired_ecb,
+            ledge_info: &mut self.ledge_information,
             prev_ecb: &self.prev_ecb,
             stage_collision,
             leave_ground_ecb_lock_duration: game_settings
                 .fighter_common
                 .leave_ground_ecb_frame_lock_duration,
             downward_stick_threshold: game_settings.input_common.run_stick_threshold,
+            fighter_ledge_collision_box,
+            waveland_snap_distance: game_settings.fighter_common.waveland_snap_distance,
         }
     }
 }
@@ -432,6 +531,7 @@ pub struct StatefulFighterQuery {
 pub fn state_update_system(
     mut query: Query<StatefulFighterQuery>,
     game_settings: Res<GameSettings>,
+    stage_collision: Res<StageCollision>,
     attack_scripts: Res<Assets<FighterAttackScript>>,
     manifests: Res<Assets<FighterManifest>>,
 ) {
@@ -455,6 +555,7 @@ pub fn state_update_system(
             &manifest.attributes,
             &attack_scripts,
             &fighter.attack_script_assets,
+            &stage_collision,
         );
         state.update(&mut update_ctx);
     }
@@ -466,7 +567,10 @@ fn transition_state(
     frame: &mut FighterFrameQueryItem,
     attributes: &FighterAttributes,
     attack_script_assets: &FighterAttackScriptAssets,
+    stage_collision: &StageCollision,
     game_settings: &GameSettings,
+    baked_animations: &BakedFighterAnimations,
+    model_scale: FGi32,
 ) {
     let old_name = current.name();
     let new_name = next.name();
@@ -480,7 +584,14 @@ fn transition_state(
                 .leave_ground_ecb_frame_lock_duration,
         );
     }
-    next.on_enter(&mut frame.enter_context(attributes, attack_script_assets, game_settings));
+    next.on_enter(&mut frame.enter_context(
+        attributes,
+        attack_script_assets,
+        game_settings,
+        stage_collision,
+        baked_animations,
+        model_scale,
+    ));
     *current = next;
     info!("{} -> {}", old_name, new_name);
 }
@@ -508,6 +619,9 @@ pub fn state_interrupt_system(
         let manifest = fighter_manifests
             .get(&fighter.manifest)
             .expect("Fighter manifest should be valid");
+        let baked = baked_animations
+            .get(&animations.baked)
+            .expect("Animation should exist");
 
         let new_state = if let Some(reaction) = pending_hit_reaction.take() {
             hitstop.remaining_frames = *reaction.victim_hitstop_frames;
@@ -554,9 +668,16 @@ pub fn state_interrupt_system(
             }
 
             info!("Entering hitstop kind: {:?}", hitstop_kind);
+            let stack_previous_knockback = !frame.surface.is_grounded()
+                && !frame.knockback_velocity.0.length_squared().is_zero()
+                && frame
+                    .knockback_state
+                    .can_stack(game_settings.fighter_common.knockback_stacking_window);
+
             Some(FighterState::Hitstun(HitstunState::new(
                 reaction,
                 hitstop_kind,
+                stack_previous_knockback,
             )))
         } else if hitstop.remaining_frames > 0 {
             None
@@ -579,7 +700,10 @@ pub fn state_interrupt_system(
                 &mut frame,
                 &manifest.attributes,
                 attack_script_assets,
+                &stage_collision,
                 &game_settings,
+                baked,
+                manifest.model_scale,
             );
         };
     }
@@ -594,6 +718,7 @@ pub fn state_collision_interrupt_system(
     mut match_state: ResMut<MatchState>,
     stage_registry: Res<StageManifestRegistry>,
     stage_manifests: Res<Assets<StageManifest>>,
+    baked_animations: Res<Assets<BakedFighterAnimations>>,
 ) {
     let Some(stage_manifest_handle) = stage_registry.get(match_config.stage) else {
         return;
@@ -608,6 +733,7 @@ pub fn state_collision_interrupt_system(
             mut state,
             mut frame,
             fighter,
+            animations,
             attack_script_assets,
             mut hitstop,
             mut pending_respawn,
@@ -619,6 +745,9 @@ pub fn state_collision_interrupt_system(
         let manifest = fighter_manifests
             .get(&fighter.manifest)
             .expect("Fighter manifest should be valid");
+        let baked = baked_animations
+            .get(&animations.baked)
+            .expect("Animation should exist");
 
         if pending_respawn.0 {
             **pending_respawn = false;
@@ -644,6 +773,8 @@ pub fn state_collision_interrupt_system(
 
             // Clear hitstop
             hitstop.remaining_frames = 0;
+            frame.knockback_velocity.0 = FGVec2::ZERO;
+            frame.knockback_state.clear();
 
             // subtract one stock
 
@@ -658,6 +789,9 @@ pub fn state_collision_interrupt_system(
 
             // reset percentage
             *damage = FighterDamage::default();
+            // reset ledge
+
+            *frame.ledge_information = FighterLedgeInformation::default();
 
             transition_state(
                 &mut state,
@@ -665,7 +799,10 @@ pub fn state_collision_interrupt_system(
                 &mut frame,
                 &manifest.attributes,
                 attack_script_assets,
+                &stage_collision,
                 &game_settings,
+                baked,
+                manifest.model_scale,
             );
             continue;
         }
@@ -675,7 +812,7 @@ pub fn state_collision_interrupt_system(
         }
 
         let new_state = state.check_collision_interrupt(
-            &mut frame.collision_context(&stage_collision, &game_settings),
+            &mut frame.collision_context(&stage_collision, manifest, &game_settings),
         );
         if let Some(new_state) = new_state {
             transition_state(
@@ -684,8 +821,97 @@ pub fn state_collision_interrupt_system(
                 &mut frame,
                 &manifest.attributes,
                 &attack_script_assets,
+                &stage_collision,
                 &game_settings,
+                baked,
+                manifest.model_scale,
             );
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::fighter::ecb::FighterPreviousECB;
+    use crate::stage::line::{StageLedge, StageLedgeSide, StageVertexID};
+
+    #[test]
+    fn animation_positions_map_forward_to_facing_and_preserve_height() {
+        let position = FGVec3::lit("99", "3", "5");
+
+        assert_eq!(
+            animation_position_to_gameplay(position, &FighterFacingDirection::Right),
+            FGVec2::lit("5", "3")
+        );
+        assert_eq!(
+            animation_position_to_gameplay(position, &FighterFacingDirection::Left),
+            FGVec2::lit("-5", "3")
+        );
+    }
+
+    #[test]
+    fn ledge_lockout_suppresses_ledge_collision() {
+        let ledge_id = StageVertexID {
+            polygon: 0,
+            vertex: 0,
+        };
+        let stage_collision = StageCollision {
+            ledges: vec![StageLedge {
+                id: ledge_id,
+                position: FGVec2::ZERO,
+                hang_side: StageLedgeSide::Left,
+            }],
+            ..default()
+        };
+        let previous_translation = FighterPreviousTranslation::default();
+        let input = FighterInput::default();
+        let mut translation = FighterTranslation::default();
+        let mut velocity = FighterVelocity::default();
+        let mut knockback_velocity = FighterKnockbackVelocity::default();
+        let mut knockback_state = FighterKnockbackState::default();
+        let mut surface = FighterSurfaceState::default();
+        let mut ecb = FighterECB::default();
+        let mut desired_ecb = FighterDesiredECB {
+            top: FGVec2::lit("0", "2"),
+            bottom: FGVec2::ZERO,
+            left: FGVec2::lit("-1", "1"),
+            right: FGVec2::lit("1", "1"),
+        };
+        let mut ledge_info = FighterLedgeInformation {
+            regrab_lockout_remaining_frames: 5,
+            ..default()
+        };
+        let previous_ecb = FighterPreviousECB::from(ecb);
+        let mut presentation_snap = FighterPresentationSnap::default();
+        let context = CollisionContext {
+            translation: &mut translation,
+            prev_translation: &previous_translation,
+            input: &input,
+            velocity: &mut velocity,
+            knockback_velocity: &mut knockback_velocity,
+            knockback_state: &mut knockback_state,
+            surface: &mut surface,
+            ecb: &mut ecb,
+            desired_ecb: &mut desired_ecb,
+            ledge_info: &mut ledge_info,
+            prev_ecb: &previous_ecb,
+            stage_collision: &stage_collision,
+            leave_ground_ecb_lock_duration: 0,
+            presentation_snap: &mut presentation_snap,
+            fighter_ledge_collision_box: FGRect {
+                origin: FGVec2::lit("-1", "1"),
+                end: FGVec2::lit("1", "-1"),
+            },
+            downward_stick_threshold: FGi32::ONE,
+            waveland_snap_distance: FGi32::ZERO,
+        };
+
+        assert!(context.air_collide_with_ledges().is_none());
+        context.ledge_info.regrab_lockout_remaining_frames = 0;
+        assert_eq!(
+            context.air_collide_with_ledges().map(|result| result.ledge),
+            Some(ledge_id)
+        );
+    }
+}

src/fighter/state/platform_pass.rs

@@ -46,7 +46,10 @@ impl FighterStateImpl for PlatformPassState {
         air::collision_interrupt(
             state_context,
             crate::fighter::state::land::LandingType::Normal,
-            true,
+            crate::fighter::collision::AirCollisionOptions {
+                can_pass_through_soft_platforms: true,
+                ..Default::default()
+            },
         )
     }
     

src/fighter/surface.rs

@@ -1,6 +1,6 @@
 use bevy::prelude::*;
 
-use crate::stage::line::StageLineID;
+use crate::{fighter::FighterLedgeInformation, stage::line::StageLineID};
 
 #[derive(Clone, Copy, Debug, Hash, PartialEq, Eq)]
 pub enum EcbLockPolicy {
@@ -53,8 +53,9 @@ impl FighterSurfaceState {
         }
     }
 
-    pub(crate) fn land(&mut self, line_id: StageLineID) {
+    pub(crate) fn land(&mut self, line_id: StageLineID, ledge_info: &mut FighterLedgeInformation) {
         *self = Self::Grounded { line_id };
+        ledge_info.grab_count = 0;
     }
 
     pub fn clear_polygon_ignore(&mut self, polygon: usize) {
@@ -151,7 +152,11 @@ mod tests {
             polygon: 2,
             segment: 3,
         };
-        surface.land(line_id);
+        let mut ledge_info = FighterLedgeInformation {
+            regrab_lockout_remaining_frames: 0,
+            grab_count: 0,
+        };
+        surface.land(line_id, &mut ledge_info);
         assert!(surface.is_grounded());
         assert_eq!(surface.line_id(), Some(line_id));
 
@@ -220,8 +225,11 @@ mod tests {
         surface.ignore_polygon(3, 5);
         surface.apply_airborne_policy(EcbLockPolicy::Restart, 2);
         assert!(surface.is_polygon_ignored(3));
-
+        let mut ledge_info = FighterLedgeInformation {
-        surface.land(StageLineID { polygon: 0, segment: 0 });
+            regrab_lockout_remaining_frames: 0,
+            grab_count: 0,
+        };
+        surface.land(StageLineID { polygon: 0, segment: 0 }, &mut ledge_info);
         assert!(!surface.is_polygon_ignored(3));
     }
 }

src/game_settings.rs

@@ -18,6 +18,7 @@ pub struct FighterSettingsCommon {
 
     /// Ground friction applied when the fighter is above the walk speed
     pub ground_friction_over_walk_speed_multiplier: FGi32,
+    /// Minimum active launch frames between hits before airborne knockback stacks.
     pub knockback_stacking_window: u32,
     pub knockback_decay_per_frame: FGi32,
 
@@ -51,6 +52,13 @@ pub struct FighterSettingsCommon {
     
     pub angel_platform_invulnerability_duration: u32,
     
+    /// Frames during which a fighter cannot grab any ledge after dropping from one.
+    pub ledge_drop_regrab_lockout_duration_frames: u32,
+    /// How many frames (+ the ledge animation duration) the fighter will be invulnerable after grabbing the ledge
+    pub ledge_grab_invulnerability_duration: u32,
+    /// How many times the fighter can grab the ledge without landing and still get invulnerability
+    pub max_ledge_grab_count: u32,
+
     /// When hit while the receiver is in the air, use this angle
     pub sakurai_angle_aerial_angle: FGi32,
     /// When hit while the receiver is in the ground and at low knockback, use this angle
@@ -59,6 +67,8 @@ pub struct FighterSettingsCommon {
     pub sakurai_angle_high_knockback_angle: FGi32,
     /// past this threshold, the knockback is considered high, so it will use [sakurai_angle_high_knockback_angle]
     pub sakurai_angle_knockback_threshold: FGi32,
+
+    pub waveland_snap_distance: FGi32,
 }
 #[derive(Reflect, Serialize, Deserialize, Clone)]
 #[reflect(opaque)]

src/hitbox_viewer/mod.rs

@@ -10,6 +10,7 @@ use bevy::{
     world_serialization::WorldAssetRoot,
 };
 use bevy_egui::{EguiContexts, EguiPrimaryContextPass, egui};
+use bevy_ggrs::SnapshotPlugin;
 use clap::{Parser, ValueEnum};
 use egui_extras::Column;
 use itertools::Itertools;
@@ -131,6 +132,7 @@ impl Plugin for HitboxViewerPlugin {
             )
         };
         app.add_plugins((
+            SnapshotPlugin,
             GameAssetPlugin,
             FighterScriptImportPlugin,
             BakedAnimationAssetProcessingPlugin,

src/input/buffer.rs

@@ -717,7 +717,6 @@ pub fn postprocess_input(
                 FighterAttackCommandType::Neutral
             };
 
-            dbg!(input.movement_flick.y, attack_type);
             input.set_lifetime(FighterCommands::Attack, tap);
             input.set_attack_command_type(attack_type);
         }

src/materials/fighter_material.rs

@@ -1,10 +1,17 @@
-use bevy::{gltf::GltfMaterialName, pbr::{ExtendedMaterial, MaterialExtension}, prelude::*, render::render_resource::AsBindGroup, shader::ShaderRef, world_serialization::WorldInstanceReady};
+use bevy::{
+    gltf::GltfMaterialName,
+    pbr::{ExtendedMaterial, MaterialExtension},
+    prelude::*,
+    render::render_resource::AsBindGroup,
+    shader::ShaderRef,
+    world_serialization::WorldInstanceReady,
+};
 
 pub type FighterMaterial = ExtendedMaterial<StandardMaterial, FighterMaterialExtension>;
 
 #[derive(Component)]
 pub struct FighterMesh {
-    pub fighter: Entity
+    pub fighter: Entity,
 }
 
 #[derive(Asset, AsBindGroup, Reflect, Debug, Clone, Default)]
@@ -64,12 +71,22 @@ pub fn bind_fighter_material(
             continue;
         };
 
-        commands.entity(entity).insert((MeshMaterial3d(asset_materials.add(ExtendedMaterial {
+        commands
-            base: StandardMaterial {
+            .entity(entity)
-                // can be used in forward or deferred mode
+            .remove::<MeshMaterial3d<StandardMaterial>>()
-                ..original_material.clone()
+            .insert((
-            },
+                MeshMaterial3d(asset_materials.add(ExtendedMaterial {
-            extension: FighterMaterialExtension::new(bevy::color::palettes::css::BLUE.into())
+                    base: StandardMaterial {
-        })), FighterMesh { fighter: scene_ready.entity  }));
+                        // can be used in forward or deferred mode
+                        ..original_material.clone()
+                    },
+                    extension: FighterMaterialExtension::new(
+                        bevy::color::palettes::css::BLUE.into(),
+                    ),
+                })),
+                FighterMesh {
+                    fighter: scene_ready.entity,
+                },
+            ));
     }
 }

src/math/mod.rs

@@ -3,3 +3,4 @@ pub mod segment;
 pub mod vec;
 pub mod fixed_transform;
 pub mod vec3;
+pub mod rect;

src/math/rect.rs

@@ -0,0 +1,12 @@
+use crate::math::vec::FGVec2;
+
+pub struct FGRect {
+    pub origin: FGVec2,
+    pub end: FGVec2,
+}
+
+impl FGRect {
+    pub fn contains_point(&self, point: FGVec2) -> bool {
+        point.x >= self.origin.x && point.y <= self.origin.y && point.x <= self.end.x && point.y >= self.end.y
+    }
+}

src/stage/debug.rs

@@ -1,15 +1,15 @@
 use bevy::{color::palettes::css::RED, prelude::*};
 
 use crate::{
-    match_loading::MatchConfig, math::{int::FGi32, vec3::FGVec3}, stage::{
+    game_settings::GameSettings, match_loading::MatchConfig, math::{int::FGi32, vec3::FGVec3}, stage::{
-        line::StageCollision,
+        line::{StageCollision, StageLedgeSide, StagePolyLineSegmentType}, manifest::{StageManifest, StageManifestRegistry},
-        manifest::{StageManifest, StageManifestRegistry},
     },
 };
 
-pub fn debug_draw_scene(mut gizmos: Gizmos, stage_collision: Res<StageCollision>) {
+pub fn debug_draw_scene(mut gizmos: Gizmos, stage_collision: Res<StageCollision>, game_settings: Res<GameSettings>) {
     for poly in stage_collision.stage_polys.iter() {
-        for segment in poly.segments.iter() {
+        for (segment, next_segment) in poly.segments.iter().zip(poly.segments.iter().cycle().skip(1)) {
+            let wavedash_normal = ((next_segment.normal.to_vec2() + segment.normal.to_vec2()) * 0.5).normalize();
             let from = segment.segment.point1().to_vec2();
             let to = segment.segment.point2().to_vec2();
             let from_3d = Vec3::new(from.x, from.y, 0.0);
@@ -18,8 +18,32 @@ pub fn debug_draw_scene(mut gizmos: Gizmos, stage_collision: Res<StageCollision>
             gizmos.line(from_3d, end_3d, RED);
             let midpoint = (from_3d + end_3d) * 0.5;
             gizmos.arrow(midpoint, midpoint + normal_3d, RED);
+            if matches!(segment.segment_type, StagePolyLineSegmentType::Floor) {
+                let radius = game_settings.fighter_common.waveland_snap_distance.to_num::<f32>();
+                let a = segment.segment.point1().to_vec2();
+                let a = Vec3::new(a.x, a.y, 0.0);
+                let b = segment.segment.point2().to_vec2();
+                let b = Vec3::new(b.x, b.y, 0.0);
+                let offset = Vec3::new(wavedash_normal.x, wavedash_normal.y, 0.0) * radius;
+                gizmos.line(a + offset, b + offset, bevy::color::palettes::css::HOT_PINK);
+                gizmos.line(a - offset, b - offset, bevy::color::palettes::css::HOT_PINK);
+            }
         }
     }
+
+    for ledge in &stage_collision.ledges {
+        let position = ledge.position.to_vec2().extend(0.0);
+        let direction = match ledge.hang_side {
+            StageLedgeSide::Left => Vec3::NEG_X,
+            StageLedgeSide::Right => Vec3::X,
+        };
+        gizmos.circle(position, 1.5, bevy::color::palettes::css::LIME);
+        gizmos.arrow(
+            position,
+            position + direction * 4.0,
+            bevy::color::palettes::css::LIME,
+        );
+    }
 }
 
 pub fn debug_draw_blast_zones(

src/stage/line.rs

@@ -3,7 +3,7 @@
 use bevy::prelude::*;
 use serde::{Deserialize, Serialize};
 
-use crate::math::{segment::FGSegment2d, vec::FGVec2};
+use crate::math::{rect::FGRect, segment::FGSegment2d, vec::FGVec2};
 
 #[derive(Reflect, Clone, Copy, PartialEq, Serialize, Deserialize)]
 pub enum StagePolyLineSegmentType {
@@ -32,6 +32,27 @@ pub struct StageLineID {
     pub segment: usize,
 }
 
+/// Identifies a corner in the stage collision geometry.
+#[derive(Reflect, Hash, Debug, Clone, Copy, Default, PartialEq, Eq)]
+pub struct StageVertexID {
+    pub polygon: usize,
+    pub vertex: usize,
+}
+
+/// The side of a ledge on which a grabbing fighter hangs.
+#[derive(Reflect, Serialize, Deserialize, Hash, Debug, Clone, Copy, PartialEq, Eq)]
+pub enum StageLedgeSide {
+    Left,
+    Right,
+}
+
+#[derive(Reflect, Hash, Debug, Clone, Copy, PartialEq)]
+pub struct StageLedge {
+    pub id: StageVertexID,
+    pub position: FGVec2,
+    pub hang_side: StageLedgeSide,
+}
+
 #[derive(Reflect, Clone, Default)]
 pub struct StagePoly {
     pub poly_type: StagePolyType,
@@ -44,10 +65,65 @@ pub struct StagePlaneIntersectResult {
     pub normal: FGVec2,
 }
 
+pub struct StageLedgeIntersectResult {
+    pub vertex_id: StageVertexID,
+    pub ledge_idx: usize
+}
+
+
 #[derive(Resource, Reflect, Clone, Default)]
 #[reflect(Resource)]
 pub struct StageCollision {
     pub stage_polys: Vec<StagePoly>,
+    pub ledges: Vec<StageLedge>,
+}
+
+impl StageCollision {
+    pub fn intersect_ledges(&self, ledge_grab_box: &FGRect) -> Option<StageLedgeIntersectResult> {
+        for (ledge_idx, ledge) in self.ledges.iter().enumerate() {
+            if ledge_grab_box.contains_point(ledge.position) {
+                return Some(StageLedgeIntersectResult {
+                    vertex_id: ledge.id,
+                    ledge_idx
+                });
+            }
+        }
+        None
+    }
+
+    pub fn find_ledge_by_vertex(&self, vertex: StageVertexID) -> Option<&StageLedge> {
+        self.ledges.iter().find(|ledge| ledge.id == vertex)
+    }
+
+    /// Returns the walkable segment on the stage side of a ledge.
+    pub fn find_ledge_ground_segment(
+        &self,
+        vertex: StageVertexID,
+    ) -> Option<(StageLineID, &StagePolyLineSegment)> {
+        let ledge = self.find_ledge_by_vertex(vertex)?;
+        let polygon = self.stage_polys.get(vertex.polygon)?;
+        let segment = match ledge.hang_side {
+            StageLedgeSide::Left => vertex.vertex,
+            StageLedgeSide::Right => {
+                if vertex.vertex > 0 {
+                    vertex.vertex - 1
+                } else if matches!(polygon.poly_type, StagePolyType::Closed) {
+                    polygon.segments.len().checked_sub(1)?
+                } else {
+                    return None;
+                }
+            }
+        };
+        let line_id = StageLineID {
+            polygon: vertex.polygon,
+            segment,
+        };
+        Some((line_id, polygon.get_segment(segment)?))
+    }
+
+    pub fn get_segment(&self, segment: StageLineID) -> Option<&StagePolyLineSegment> {
+        self.stage_polys.get(segment.polygon).map(|poly| poly.segments.get(segment.segment))?
+    }
 }
 
 impl StagePoly {

src/stage/manifest.rs

@@ -9,7 +9,10 @@ use strum_macros::EnumIter;
 use crate::{
     AppState, game_settings::GameSettings, math::{vec::FGVec2}, stage::{
         StagePoly,
-        line::{StageCollision, StagePolyLineSegmentType, StagePolyType},
+        line::{
+            StageCollision, StageLedge, StageLedgeSide, StagePolyLineSegment,
+            StagePolyLineSegmentType, StagePolyType, StageVertexID,
+        },
     }, texture_reference::TextureReference,
 };
 use bevy::prelude::*;
@@ -71,6 +74,16 @@ pub enum StageId {
 pub struct StagePolyDefinition {
     poly_type: StagePolyType,
     lines: Vec<(FGVec2, StagePolyLineSegmentType)>,
+    #[serde(default)]
+    ledges: Vec<StageLedgeDefinition>,
+}
+
+#[derive(Serialize, Deserialize, Clone, Copy, Reflect)]
+pub struct StageLedgeDefinition {
+    /// Index into the polygon's `lines`, identifying the corner position.
+    vertex: usize,
+    /// Side of the corner on which a grabbing fighter will hang.
+    hang_side: StageLedgeSide,
 }
 
 #[derive(Deserialize, Clone, Asset, Reflect, RonAsset)]
@@ -176,6 +189,13 @@ pub fn prepare_stage_manifests(
             );
             return;
         }
+        if let Err(error) = manifest.validate_ledges() {
+            fail(
+                &mut next_state,
+                &format!("{:?} has invalid ledges: {error}", manifest.id),
+            );
+            return;
+        }
         if registry.insert(manifest.id, handle.clone()).is_some() {
             fail(
                 &mut next_state,
@@ -267,6 +287,14 @@ impl StageManifest {
         Ok(())
     }
 
+    fn validate_ledges(&self) -> Result<(), String> {
+        for (polygon_index, definition) in self.polygons.iter().enumerate() {
+            definition.validate_ledges(polygon_index)?;
+        }
+
+        Ok(())
+    }
+
     pub fn to_collision(&self) -> StageCollision {
         let stage_polys: Vec<StagePoly> = self
             .polygons
@@ -274,7 +302,84 @@ impl StageManifest {
             .map(|def| StagePoly::build(def.poly_type, &def.lines))
             .collect();
 
-        StageCollision { stage_polys }
+        let ledges = self
+            .polygons
+            .iter()
+            .enumerate()
+            .flat_map(|(polygon, definition)| definition.resolved_ledges(polygon))
+            .collect();
+
+        StageCollision {
+            stage_polys,
+            ledges,
+        }
+    }
+}
+
+impl StagePolyDefinition {
+    fn validate_ledges(&self, polygon_index: usize) -> Result<(), String> {
+        let polygon = StagePoly::build(self.poly_type, &self.lines);
+        let mut vertices = HashSet::with_capacity(self.ledges.len());
+
+        for ledge in &self.ledges {
+            if ledge.vertex >= self.lines.len() {
+                return Err(format!(
+                    "polygon {polygon_index} references missing vertex {}",
+                    ledge.vertex
+                ));
+            }
+            if !vertices.insert(ledge.vertex) {
+                return Err(format!(
+                    "polygon {polygon_index} defines vertex {} as a ledge more than once",
+                    ledge.vertex
+                ));
+            }
+
+            let outgoing = polygon.get_segment(ledge.vertex);
+            let incoming_index = if ledge.vertex > 0 {
+                Some(ledge.vertex - 1)
+            } else if matches!(self.poly_type, StagePolyType::Closed) {
+                polygon.segments.len().checked_sub(1)
+            } else {
+                None
+            };
+            let incoming = incoming_index.and_then(|index| polygon.get_segment(index));
+            let is_walkable_floor = |segment: Option<&StagePolyLineSegment>| {
+                segment.is_some_and(|segment| {
+                    segment.segment_type == StagePolyLineSegmentType::Floor
+                        && segment.normal.y > crate::math::int::FGi32::ZERO
+                })
+            };
+            let (interior, exterior) = match ledge.hang_side {
+                StageLedgeSide::Left => (outgoing, incoming),
+                StageLedgeSide::Right => (incoming, outgoing),
+            };
+            if !is_walkable_floor(interior) {
+                return Err(format!(
+                    "polygon {polygon_index} vertex {} has no upward-facing floor opposite its {:?} hang side",
+                    ledge.vertex, ledge.hang_side
+                ));
+            }
+            if is_walkable_floor(exterior) {
+                return Err(format!(
+                    "polygon {polygon_index} vertex {} is between two walkable floors rather than at an exposed corner",
+                    ledge.vertex
+                ));
+            }
+        }
+
+        Ok(())
+    }
+
+    fn resolved_ledges(&self, polygon: usize) -> impl Iterator<Item = StageLedge> + '_ {
+        self.ledges.iter().map(move |ledge| StageLedge {
+            id: StageVertexID {
+                polygon,
+                vertex: ledge.vertex,
+            },
+            position: self.lines[ledge.vertex].0,
+            hang_side: ledge.hang_side,
+        })
     }
 }
 
@@ -319,3 +424,115 @@ impl StageCameraProfile {
                 < 90.0
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::stage::line::StageLineID;
+
+    fn platform(ledges: Vec<StageLedgeDefinition>) -> StagePolyDefinition {
+        StagePolyDefinition {
+            poly_type: StagePolyType::Platform,
+            lines: vec![
+                (FGVec2::lit("-5", "0"), StagePolyLineSegmentType::Floor),
+                (FGVec2::lit("5", "0"), StagePolyLineSegmentType::Floor),
+            ],
+            ledges,
+        }
+    }
+
+    #[test]
+    fn platform_endpoints_can_be_defined_as_ledges() {
+        let definition = platform(vec![
+            StageLedgeDefinition {
+                vertex: 0,
+                hang_side: StageLedgeSide::Left,
+            },
+            StageLedgeDefinition {
+                vertex: 1,
+                hang_side: StageLedgeSide::Right,
+            },
+        ]);
+
+        assert_eq!(definition.validate_ledges(3), Ok(()));
+        let ledges = definition.resolved_ledges(3).collect::<Vec<_>>();
+        assert_eq!(ledges[0].id, StageVertexID { polygon: 3, vertex: 0 });
+        assert_eq!(ledges[0].position, FGVec2::lit("-5", "0"));
+        assert_eq!(ledges[1].id, StageVertexID { polygon: 3, vertex: 1 });
+        assert_eq!(ledges[1].position, FGVec2::lit("5", "0"));
+    }
+
+    #[test]
+    fn ledge_ground_segments_point_toward_the_stage_interior() {
+        let definition = platform(vec![
+            StageLedgeDefinition {
+                vertex: 0,
+                hang_side: StageLedgeSide::Left,
+            },
+            StageLedgeDefinition {
+                vertex: 1,
+                hang_side: StageLedgeSide::Right,
+            },
+        ]);
+        let collision = StageCollision {
+            stage_polys: vec![StagePoly::build(definition.poly_type, &definition.lines)],
+            ledges: definition.resolved_ledges(0).collect(),
+        };
+
+        for vertex in [0, 1] {
+            let (line_id, segment) = collision
+                .find_ledge_ground_segment(StageVertexID { polygon: 0, vertex })
+                .unwrap();
+            assert_eq!(line_id, StageLineID { polygon: 0, segment: 0 });
+            assert!(matches!(
+                segment.segment_type,
+                StagePolyLineSegmentType::Floor
+            ));
+        }
+    }
+
+    #[test]
+    fn invalid_and_duplicate_ledge_vertices_are_rejected() {
+        let missing = platform(vec![StageLedgeDefinition {
+            vertex: 2,
+            hang_side: StageLedgeSide::Right,
+        }]);
+        assert!(missing.validate_ledges(0).is_err());
+
+        let duplicate = platform(vec![
+            StageLedgeDefinition {
+                vertex: 0,
+                hang_side: StageLedgeSide::Left,
+            },
+            StageLedgeDefinition {
+                vertex: 0,
+                hang_side: StageLedgeSide::Right,
+            },
+        ]);
+        assert!(duplicate.validate_ledges(0).is_err());
+    }
+
+    #[test]
+    fn ledge_must_border_an_upward_facing_floor() {
+        let definition = StagePolyDefinition {
+            poly_type: StagePolyType::Platform,
+            lines: vec![
+                (FGVec2::lit("0", "0"), StagePolyLineSegmentType::Wall),
+                (FGVec2::lit("0", "5"), StagePolyLineSegmentType::Wall),
+            ],
+            ledges: vec![StageLedgeDefinition {
+                vertex: 0,
+                hang_side: StageLedgeSide::Left,
+            }],
+        };
+
+        assert!(definition.validate_ledges(0).is_err());
+
+        let wrong_side = platform(vec![StageLedgeDefinition {
+            vertex: 0,
+            hang_side: StageLedgeSide::Right,
+        }]);
+        assert!(wrong_side.validate_ledges(0).is_err());
+    }
+
+}