Fix bone resampling breaking hitbox interpolation (#73)

Reviewed-on: #73
Co-authored-by: Álex Román Núñez <eirexe@eirteam.moe>

src/debug_tools.rs

@@ -109,7 +109,9 @@ impl FighterDebugRowKind {
 enum DebugFlag {
     Network,
     Ecb,
+    BlastZones,
     StageCollision,
+    SpawnPositions,
     AnimationBones,
     AttackHitboxes,
     Hurtboxes,
@@ -173,6 +175,14 @@ const WORLD_MENU: &[DebugMenuEntry] = &[
         label: "Stage collision",
         flag: DebugFlag::StageCollision,
     },
+    DebugMenuEntry::Toggle {
+        label: "Blast zones",
+        flag: DebugFlag::BlastZones,
+    },
+    DebugMenuEntry::Toggle {
+        label: "Spawn points",
+        flag: DebugFlag::SpawnPositions,
+    },
     DebugMenuEntry::GameSpeed {
         label: "Game speed",
     },
@@ -243,7 +253,9 @@ pub struct DebugSettings {
     pub frame_stepping: bool,
     pub network: bool,
     pub ecb: bool,
+    pub blast_zones: bool,
     pub stage_collision: bool,
+    pub spawn_positions: bool,
     pub animation_bones: bool,
     pub attack_hitboxes: bool,
     pub hurtboxes: bool,
@@ -264,7 +276,9 @@ impl Default for DebugSettings {
             frame_stepping: false,
             network: false,
             ecb: false,
+            blast_zones: false,
             stage_collision: false,
+            spawn_positions: false,
             animation_bones: false,
             attack_hitboxes: false,
             hurtboxes: false,
@@ -328,6 +342,8 @@ impl DebugSettings {
         match flag {
             DebugFlag::Network => self.network,
             DebugFlag::Ecb => self.ecb,
+            DebugFlag::BlastZones => self.blast_zones,
+            DebugFlag::SpawnPositions => self.spawn_positions,
             DebugFlag::StageCollision => self.stage_collision,
             DebugFlag::AnimationBones => self.animation_bones,
             DebugFlag::AttackHitboxes => self.attack_hitboxes,
@@ -342,7 +358,9 @@ impl DebugSettings {
         match flag {
             DebugFlag::Network => self.network = !self.network,
             DebugFlag::Ecb => self.ecb = !self.ecb,
+            DebugFlag::BlastZones => self.blast_zones = !self.blast_zones,
             DebugFlag::StageCollision => self.stage_collision = !self.stage_collision,
+            DebugFlag::SpawnPositions => self.spawn_positions = !self.spawn_positions,
             DebugFlag::AnimationBones => self.animation_bones = !self.animation_bones,
             DebugFlag::AttackHitboxes => self.attack_hitboxes = !self.attack_hitboxes,
             DebugFlag::Hurtboxes => self.hurtboxes = !self.hurtboxes,
@@ -884,6 +902,14 @@ pub fn stage_collision_enabled(settings: Res<DebugSettings>) -> bool {
     settings.stage_collision
 }
 
+pub fn blast_zones_enabled(settings: Res<DebugSettings>) -> bool {
+    settings.blast_zones
+}
+
+pub fn spawn_positions_enabled(settings: Res<DebugSettings>) -> bool {
+    settings.spawn_positions
+}
+
 pub fn animation_bones_enabled(settings: Res<DebugSettings>) -> bool {
     settings.animation_bones
 }

src/debug_tools/save_state.rs

@@ -1,22 +1,12 @@
 use bevy::prelude::*;
 
 use crate::{
-    camera::MatchCamera,
+    camera::MatchCamera, fighter::{
-    fighter::{
+        FighterECB, FighterFacingDirection, FighterHitboxes, FighterHitstop, FighterHitstopShake, FighterPendingRespawn, FighterPreviousFacingDirection, FighterPreviousTranslation, FighterSurfaceState, FighterTranslation, FighterVelocity, animation::FighterAnimationFrame, attack::{
-        FighterECB, FighterFacingDirection, FighterHitboxes, FighterHitstop, FighterHitstopShake,
-        FighterPreviousFacingDirection, FighterPreviousTranslation, FighterSurfaceState,
-        FighterTranslation, FighterVelocity,
-        animation::FighterAnimationFrame,
-        attack::{
             FighterDamage, FighterKnockbackVelocity, FighterPendingHitReaction, FighterPendingHits,
             FighterSolvedHurtboxes, FighterStaleMoveQueue,
-        },
+        }, baked_animation::FighterBoneMatrices, state::FighterState,
-        baked_animation::FighterBoneMatrices,
+    }, input::FighterInput, match_runtime::MatchState, player::Player, stage::line::StageCollision,
-        state::FighterState,
-    },
-    input::FighterInput,
-    player::Player,
-    stage::line::StageCollision,
 };
 
 #[derive(Resource, Default)]
@@ -29,6 +19,7 @@ struct Checkpoint {
     fighters: Vec<FighterCheckpoint>,
     stage_collision: StageCollision,
     pending_hits: FighterPendingHits,
+    match_state: MatchState,
 }
 
 #[derive(Clone)]
@@ -55,6 +46,7 @@ struct FighterCheckpoint {
     solved_hurtboxes: FighterSolvedHurtboxes,
     bone_matrices: FighterBoneMatrices,
     surface: FighterSurfaceState,
+    pending_respawn: FighterPendingRespawn,
 }
 
 pub(super) fn save_or_restore(world: &mut World) {
@@ -99,10 +91,12 @@ pub(super) fn save_or_restore(world: &mut World) {
             checkpoint_fighters.push(checkpoint);
         }
         let pending_hits = world.resource::<FighterPendingHits>().clone();
+        let match_state = world.resource::<MatchState>().clone();
         world.resource_mut::<DebugSaveState>().checkpoint = Some(Checkpoint {
             fighters: checkpoint_fighters,
             stage_collision,
             pending_hits,
+            match_state,
         });
         info!("Saved debug game state");
         return;
@@ -154,9 +148,11 @@ pub(super) fn save_or_restore(world: &mut World) {
         entity.insert(saved.solved_hurtboxes.clone());
         entity.insert(saved.bone_matrices.clone());
         entity.insert(saved.surface.clone());
+        entity.insert(saved.pending_respawn.clone());
     }
     world.insert_resource(checkpoint.pending_hits.clone());
     world.insert_resource(checkpoint.stage_collision);
+    world.insert_resource(checkpoint.match_state);
     for mut match_camera in world.query::<&mut MatchCamera>().iter_mut(world) {
         match_camera.needs_snap = true;
     }
@@ -188,6 +184,7 @@ fn capture_fighter(world: &World, entity: Entity) -> Option<FighterCheckpoint> {
         solved_hurtboxes: fighter.get::<FighterSolvedHurtboxes>()?.clone(),
         bone_matrices: fighter.get::<FighterBoneMatrices>()?.clone(),
         surface: fighter.get::<FighterSurfaceState>()?.clone(),
+        pending_respawn: fighter.get::<FighterPendingRespawn>()?.clone(),
     })
 }
 

src/fighter/baked_animation/mod.rs

@@ -8,7 +8,7 @@ pub use crate::math::fixed_transform::FixedMat4;
 pub use asset_baking::{BakedAnimationAssetProcessingPlugin, BakedAnimationPlugin};
 pub use runtime::{
     BakedAnimationClip, BakedFighterAnimations, FighterBoneIndexMap, FighterBoneMatrices,
-    update_fighter_bone_matrices,
+    resample_fighter_bone_matrices, update_fighter_bone_matrices,
 };
 
 pub const BAKED_ANIMATION_FPS: u32 = 60;
@@ -275,6 +275,31 @@ mod tests {
         assert_eq!(capacities, matrices.buffer_capacities());
     }
 
+    #[test]
+    fn same_frame_resample_preserves_previous_gameplay_pose() {
+        let names = ["root".into()];
+        let parents = [None];
+        let mut pose_a = FixedMat4::IDENTITY;
+        pose_a.translate(FGVec3::lit("1", "0", "0"));
+        let mut pose_b = FixedMat4::IDENTITY;
+        pose_b.translate(FGVec3::lit("2", "0", "0"));
+        let mut snapped_pose = FixedMat4::IDENTITY;
+        snapped_pose.translate(FGVec3::lit("3", "0", "0"));
+        let mut matrices = FighterBoneMatrices::default();
+
+        matrices.set_pose(AnimKind::Wait, &names, &parents, &[pose_a], FGi32::ONE);
+        matrices.set_pose(AnimKind::Wait, &names, &parents, &[pose_b], FGi32::ONE);
+        matrices.resample_pose(
+            AnimKind::Landing,
+            &names,
+            &parents,
+            &[snapped_pose],
+            FGi32::ONE,
+        );
+
+        assert_eq!(matrices.get_index(0), Some((pose_a, snapped_pose)));
+    }
+
     #[test]
     fn model_scale_affects_gameplay_bones_without_changing_visual_locals() {
         let mut root = FixedMat4::IDENTITY;

src/fighter/baked_animation/runtime.rs

@@ -144,6 +144,27 @@ impl FighterBoneMatrices {
         parents: &[Option<usize>],
         local: &[FixedMat4],
         model_scale: FGi32,
+    ) {
+        self.sample_pose(kind, bone_names, parents, local, model_scale, true);
+    }
+    pub(super) fn resample_pose(
+        &mut self,
+        kind: AnimKind,
+        bone_names: &[String],
+        parents: &[Option<usize>],
+        local: &[FixedMat4],
+        model_scale: FGi32,
+    ) {
+        self.sample_pose(kind, bone_names, parents, local, model_scale, false);
+    }
+    fn sample_pose(
+        &mut self,
+        kind: AnimKind,
+        bone_names: &[String],
+        parents: &[Option<usize>],
+        local: &[FixedMat4],
+        model_scale: FGi32,
+        advance_history: bool,
     ) {
         assert_eq!(
             bone_names.len(),
@@ -167,9 +188,11 @@ impl FighterBoneMatrices {
         self.local_matrices.reserve(local.len());
         self.previous_local_matrices.reserve(local.len());
         self.model_matrices.reserve(local.len());
+        if advance_history {
             std::mem::swap(&mut self.matrices, &mut self.previous_frame_matrices);
-        let animation_changed = self.presentation_kind != Some(kind);
             std::mem::swap(&mut self.local_matrices, &mut self.previous_local_matrices);
+        }
+        let animation_changed = self.presentation_kind != Some(kind);
         self.local_matrices.clear();
         self.local_matrices.extend_from_slice(local);
         self.model_matrices.resize(local.len(), None);
@@ -215,6 +238,56 @@ pub fn update_fighter_bone_matrices(
     manifests: Res<Assets<FighterManifest>>,
 ) {
     for (frame, animations, fighter, mut matrices, mut bone_indices) in &mut fighters {
+        sample_fighter_bone_matrices(
+            frame,
+            animations,
+            fighter,
+            &mut matrices,
+            &mut bone_indices,
+            &baked_assets,
+            &manifests,
+            true,
+        );
+    }
+}
+
+/// Resamples the current pose after collision-driven state transitions without
+/// advancing the previous-frame pose used for swept gameplay volumes.
+pub fn resample_fighter_bone_matrices(
+    mut fighters: Query<(
+        &FighterAnimationFrame,
+        &FighterAnimations,
+        &Fighter,
+        &mut FighterBoneMatrices,
+        &mut FighterBoneIndexMap,
+    )>,
+    baked_assets: Res<Assets<BakedFighterAnimations>>,
+    manifests: Res<Assets<FighterManifest>>,
+) {
+    for (frame, animations, fighter, mut matrices, mut bone_indices) in &mut fighters {
+        sample_fighter_bone_matrices(
+            frame,
+            animations,
+            fighter,
+            &mut matrices,
+            &mut bone_indices,
+            &baked_assets,
+            &manifests,
+            false,
+        );
+    }
+}
+
+fn sample_fighter_bone_matrices(
+    frame: &FighterAnimationFrame,
+    animations: &FighterAnimations,
+    fighter: &Fighter,
+    matrices: &mut FighterBoneMatrices,
+    bone_indices: &mut FighterBoneIndexMap,
+    baked_assets: &Assets<BakedFighterAnimations>,
+    manifests: &Assets<FighterManifest>,
+    advance_history: bool,
+) {
     let baked = baked_assets
         .get(&animations.baked)
         .expect("fighter baked animation asset should be loaded before the match starts");
@@ -228,6 +301,7 @@ pub fn update_fighter_bone_matrices(
     let manifest = manifests
         .get(&fighter.manifest)
         .expect("fighter manifest should be loaded before the match starts");
+    if advance_history {
         matrices.set_pose(
             frame.kind,
             &baked.bone_names,
@@ -235,6 +309,15 @@ pub fn update_fighter_bone_matrices(
             pose,
             manifest.model_scale,
         );
+    } else {
+        matrices.resample_pose(
+            frame.kind,
+            &baked.bone_names,
+            &baked.parents,
+            pose,
+            manifest.model_scale,
+        );
+    }
     if bone_indices.0.is_empty() {
         bone_indices.0.extend(
             baked
@@ -245,7 +328,6 @@ pub fn update_fighter_bone_matrices(
         );
     }
 }
-}
 
 fn resolve_model_transform(
     index: usize,

src/fighter/blast_zones.rs

@@ -0,0 +1,36 @@
+//! Various interactions with the blast zones
+
+use bevy::prelude::*;
+
+use crate::{fighter::{FighterPendingRespawn, FighterTranslation, state::FighterState}, match_loading::MatchConfig, stage::manifest::{StageManifest, StageManifestRegistry}};
+
+pub fn apply_blast_zones(
+    stage_registry: Res<StageManifestRegistry>,
+    stage_manifests: Res<Assets<StageManifest>>,
+    match_config: Res<MatchConfig>,
+    fighters: Query<(&FighterTranslation, &mut FighterPendingRespawn, &FighterState)>
+) {
+    let Some(stage_manifest_handle) = stage_registry.get(match_config.stage) else {
+        return;
+    };
+
+    let Some(stage_manifest) = stage_manifests.get(&stage_manifest_handle) else {
+        return;
+    };
+
+    for (translation, mut pending_respawn, state) in fighters {
+        let is_off_the_left = translation.x < stage_manifest.blast_zone_top_left.x;
+        let is_off_the_right = translation.x > stage_manifest.blast_zone_bottom_right.x;
+        let is_off_the_top = translation.y > stage_manifest.blast_zone_top_left.y;
+        let is_off_the_bottom = translation.y < stage_manifest.blast_zone_bottom_right.y;
+        
+        if is_off_the_left || is_off_the_bottom || is_off_the_right {
+            pending_respawn.0 = true;
+        } else if is_off_the_top {
+            let is_in_hitstun = matches!(state, FighterState::Hitstun(..));
+            if is_in_hitstun {
+                pending_respawn.0 = true;
+            }
+        }
+    }
+}

src/fighter/mod.rs

@@ -20,6 +20,7 @@ pub mod motion;
 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
@@ -128,11 +129,15 @@ impl FighterFacingDirection {
 #[require(Transform)]
 pub struct FighterVisual;
 
+#[derive(Component, DerefMut, Deref, Debug, Default, Hash, Clone, Copy)]
+pub struct FighterPendingRespawn(bool);
+
 #[derive(Component)]
 #[require(
     FighterStaleMoveQueue,
     FighterDamage,
     FighterPendingHitReaction,
+    FighterPendingRespawn,
     FighterHitstop,
     FighterKnockbackVelocity,
     FighterTranslation
@@ -177,8 +182,8 @@ impl Plugin for FighterPlugin {
             .add_systems(
                 GgrsSchedule,
                 (
-                    (ecb::update_ecb, ecb::decrement_ecb_lockout, state::state_collision_interrupt_system).chain(),
+                    (blast_zones::apply_blast_zones, ecb::update_ecb, ecb::decrement_ecb_lockout, state::state_collision_interrupt_system).chain(),
-                    baked_animation::update_fighter_bone_matrices,
+                    baked_animation::resample_fighter_bone_matrices,
                 )
                     .chain()
                     .in_set(GameplaySet::Collision),
@@ -220,6 +225,8 @@ impl Plugin for FighterPlugin {
             .checksum_component_with_hash::<FighterDamage>()
             .rollback_component_with_clone::<FighterPendingHitReaction>()
             .checksum_component_with_hash::<FighterPendingHitReaction>()
+            .rollback_component_with_copy::<FighterPendingRespawn>()
+            .checksum_component_with_hash::<FighterPendingRespawn>()
             .rollback_component_with_copy::<FighterHitstop>()
             .checksum_component_with_hash::<FighterHitstop>()
             .rollback_component_with_copy::<FighterKnockbackVelocity>()
@@ -281,6 +288,7 @@ pub struct FighterHitboxes(pub Option<FighterActiveAttack>);
 pub fn spawn_fighter(
     commands: &mut Commands,
     player_handle: usize,
+    controller_port: usize,
     spawn_position: FGVec2,
     manifest: Handle<FighterManifest>,
     model_scale: FGi32,
@@ -294,6 +302,7 @@ pub fn spawn_fighter(
             Name(format!("Fighter {player_handle}").into()),
             Player {
                 handle: player_handle,
+                controller_port,
             },
             Fighter { manifest: manifest },
             FighterFacingDirection::Right,

src/fighter/state/angel.rs

@@ -0,0 +1,53 @@
+use crate::{fighter::{animation::AnimKind, state::{FighterState, FighterStateImpl, air::AirborneStateCommon, fall::FallState}}, math::vec::FGVec2};
+
+#[derive(Debug, Clone, Hash)]
+pub struct AngelState {
+    frames_remaining: u32
+}
+
+impl AngelState {
+    pub fn new(duration: u32) -> Self {
+        Self {
+            frames_remaining: duration
+        }
+    }
+}
+
+impl FighterStateImpl for AngelState {
+    const NAME: &'static str = "Angel";
+
+    fn check_interrupt(&self, state_context: &mut super::InterruptContext) -> Option<super::FighterState> {
+        let moved_sideways = !state_context.input.get_last_frame().movement.x.is_zero();
+        let moved_vertically = !state_context.input.get_last_frame().movement.y.is_zero();
+
+        if self.frames_remaining == 0 || moved_sideways || moved_vertically {
+            Some(FighterState::Fall(FallState::new(AirborneStateCommon::default())))
+        } else {
+            None
+        }
+    }
+
+    fn update(&mut self, _state_context: &mut super::UpdateContext) {
+        self.frames_remaining = self.frames_remaining.saturating_sub(1);
+    }
+
+    fn is_visually_grounded<'a>(&'a self) -> bool {
+        false
+    }
+    
+    fn on_enter(&mut self, state_context: &mut super::EnterContext) {
+        state_context.play_animation(AnimKind::Wait, true);
+        state_context.velocity.0 = FGVec2::ZERO;
+    }
+    
+    fn check_collision_interrupt(
+        &mut self,
+        _state_context: &mut super::CollisionContext,
+    ) -> Option<super::FighterState> {
+        None
+    }
+    
+    fn surface_policy(&self) -> super::SurfacePolicy {
+        super::SurfacePolicy::Airborne(crate::fighter::surface::EcbLockPolicy::Clear)
+    }
+}

src/fighter/state/mod.rs

@@ -15,22 +15,29 @@ use crate::fighter::baked_animation::BakedFighterAnimations;
 use crate::fighter::ecb::FighterPreviousECB;
 use crate::fighter::manifest::FighterManifest;
 use crate::fighter::state::hitstun::HitstunState;
+use crate::fighter::surface::EcbLockPolicy;
 use crate::fighter::visual::FighterAnimations;
 use crate::fighter::{
     Fighter, FighterECB, FighterFacingDirection, FighterHitboxes, FighterHitstop,
-    FighterHitstopShake, FighterHitstopShakeKind, FighterHitstopShakeRole,
+    FighterHitstopShake, FighterHitstopShakeKind, FighterHitstopShakeRole, FighterPendingRespawn,
-    FighterPreviousTranslation, FighterSurfaceState, FighterTranslation, FighterVelocity,
+    FighterPresentationSnap, FighterPreviousTranslation, FighterSurfaceState, FighterTranslation,
-    FighterPresentationSnap,
+    FighterVelocity, FighterDamage,
 };
-use crate::fighter::surface::EcbLockPolicy;
 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::vec::FGVec2;
+use crate::player::Player;
 use crate::scripting::FighterAttackScript;
 use crate::stage::line::StageCollision;
+use crate::stage::manifest::{StageManifest, StageManifestRegistry};
 
 pub mod air;
 pub mod air_dodge;
+pub mod angel;
+pub mod crouch;
 pub mod dash;
 pub mod fall;
 pub mod ground;
@@ -38,12 +45,11 @@ pub mod ground_attack;
 pub mod hitstun;
 pub mod jump;
 pub mod land;
+pub mod platform_pass;
 pub mod run;
 pub mod turn;
 pub mod wait;
 pub mod walk;
-pub mod crouch;
-pub mod platform_pass;
 
 #[derive(Clone, Copy, Debug, Hash, PartialEq, Eq)]
 pub enum SurfacePolicy {
@@ -210,8 +216,8 @@ impl CollisionContext<'_> {
         &self,
     ) -> Option<crate::fighter::collision::AirCollisionWithStageResult> {
         let ignored_polys = self.surface.ignored_polygon_ids();
-        let ignore_soft_platforms = self.input.get_last_frame().movement.y
+        let ignore_soft_platforms =
-            <= -self.downward_stick_threshold;
+            self.input.get_last_frame().movement.y <= -self.downward_stick_threshold;
         crate::fighter::collision::air_collide_with_stage(
             self.prev_translation,
             self.translation,
@@ -239,6 +245,7 @@ fighter_states! {
     Turn => turn::TurnState,
     GroundAttack => ground_attack::GroundAttackState,
     Hitstun => hitstun::HitstunState,
+    Angel => angel::AngelState,
 }
 
 #[derive(QueryData)]
@@ -314,7 +321,7 @@ impl<'w, 's> FighterFrameQueryItem<'w, 's> {
             surface: &mut self.surface,
             fighter_attributes: attributes,
             attack_script_assets,
-            game_settings
+            game_settings,
         }
     }
 
@@ -364,7 +371,9 @@ impl<'w, 's> FighterFrameQueryItem<'w, 's> {
             ecb: &mut self.ecb,
             prev_ecb: &self.prev_ecb,
             stage_collision,
-            leave_ground_ecb_lock_duration: game_settings.fighter_common.leave_ground_ecb_frame_lock_duration,
+            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,
         }
     }
@@ -378,9 +387,12 @@ pub struct StatefulFighterQuery {
     pub animations: &'static FighterAnimations,
     pub fighter: &'static Fighter,
     pub attack_script_assets: &'static FighterAttackScriptAssets,
+    pub player: &'static Player,
     pub pending_hit_reaction: &'static mut FighterPendingHitReaction,
     pub hitstop: &'static mut FighterHitstop,
     pub hitstop_shake: &'static mut FighterHitstopShake,
+    pub pending_respawn: &'static mut FighterPendingRespawn,
+    pub damage: &'static mut FighterDamage,
 }
 
 pub fn state_update_system(
@@ -429,7 +441,9 @@ fn transition_state(
     if let SurfacePolicy::Airborne(lock_policy) = next.surface_policy() {
         frame.surface.apply_airborne_policy(
             lock_policy,
-            game_settings.fighter_common.leave_ground_ecb_frame_lock_duration,
+            game_settings
+                .fighter_common
+                .leave_ground_ecb_frame_lock_duration,
         );
     }
     next.on_enter(&mut frame.enter_context(attributes, attack_script_assets, game_settings));
@@ -454,6 +468,7 @@ pub fn state_interrupt_system(
             mut pending_hit_reaction,
             mut hitstop,
             mut hitstop_shake,
+            ..
         } = fighter;
         let manifest = fighter_manifests
             .get(&fighter.manifest)
@@ -516,7 +531,7 @@ pub fn state_interrupt_system(
                 animations,
                 &baked_animations,
                 &manifest.attributes,
-                &stage_collision
+                &stage_collision,
             ))
         };
 
@@ -538,25 +553,89 @@ pub fn state_collision_interrupt_system(
     stage_collision: Res<StageCollision>,
     fighter_manifests: Res<Assets<FighterManifest>>,
     game_settings: Res<GameSettings>,
+    match_config: Res<MatchConfig>,
+    mut match_state: ResMut<MatchState>,
+    stage_registry: Res<StageManifestRegistry>,
+    stage_manifests: Res<Assets<StageManifest>>,
 ) {
+    let Some(stage_manifest_handle) = stage_registry.get(match_config.stage) else {
+        return;
+    };
+
+    let Some(stage_manifest) = stage_manifests.get(&stage_manifest_handle) else {
+        return;
+    };
+
     for fighter in &mut query {
         let StatefulFighterQueryItem {
             mut state,
             mut frame,
             fighter,
             attack_script_assets,
-            hitstop,
+            mut hitstop,
+            mut pending_respawn,
+            player,
+            mut damage,
             ..
         } = fighter;
-        if hitstop.remaining_frames > 0 {
-            continue;
-        }
 
         let manifest = fighter_manifests
             .get(&fighter.manifest)
             .expect("Fighter manifest should be valid");
-        let new_state =
+
-            state.check_collision_interrupt(&mut frame.collision_context(&stage_collision, &game_settings));
+        if pending_respawn.0 {
+            **pending_respawn = false;
+            let respawn_state = FighterState::Angel(angel::AngelState::new(60 * 3));
+
+            // Find the angel platform position
+            let respawn_point = stage_manifest
+                .respawn_points
+                .get(player.controller_port % stage_manifest.respawn_points.len());
+
+            if let None = respawn_point {
+                error!("Couldn't get a respawn point, falling back to the world origin");
+            }
+
+            let respawn_point = respawn_point.copied().unwrap_or(FGVec2::ZERO);
+
+            frame.translation.0 = respawn_point;
+            frame.presentation_snap.0 = true;
+
+            // Clear hitstop
+            hitstop.remaining_frames = 0;
+
+            // subtract one stock
+
+            let player_state = match_state.players.get_mut(player.handle).expect(&format!(
+                "Failed to get fighter for GGRS slot {} (controller port {})",
+                player.handle, player.controller_port
+            ));
+
+            if let Some(stocks_remaining) = &mut player_state.stocks_remaining {
+                *stocks_remaining = stocks_remaining.saturating_sub(1);
+            }
+
+            // reset percentage
+            *damage = FighterDamage::default();
+
+            transition_state(
+                &mut state,
+                respawn_state,
+                &mut frame,
+                &manifest.attributes,
+                attack_script_assets,
+                &game_settings,
+            );
+            continue;
+        }
+
+        if hitstop.remaining_frames > 0 {
+            continue;
+        }
+
+        let new_state = state.check_collision_interrupt(
+            &mut frame.collision_context(&stage_collision, &game_settings),
+        );
         if let Some(new_state) = new_state {
             transition_state(
                 &mut state,

src/input/mod.rs

@@ -28,7 +28,7 @@ pub enum LocalInputSource {
     Gamepad(Entity),
 }
 
-/// Maps an input source to a player index
+/// Persistent mapping from physical/menu controller slots to input sources.
 #[derive(Resource, Clone, Debug, Default, Deref, DerefMut)]
 pub struct LocalInputAssignments(pub Vec<(usize, LocalInputSource)>);
 
@@ -50,6 +50,16 @@ impl LocalInputAssignments {
     }
 }
 
+/// Match-local mapping from dense GGRS handles to physical input sources.
+#[derive(Resource, Clone, Debug, Default, Deref, DerefMut)]
+pub struct MatchInputAssignments(pub Vec<Option<LocalInputSource>>);
+
+impl MatchInputAssignments {
+    pub fn get_for_handle(&self, handle: usize) -> Option<LocalInputSource> {
+        self.0.get(handle).copied().flatten()
+    }
+}
+
 use crate::game_settings::GameSettings;
 use crate::math::int::FGi32;
 use crate::netcode::GGRSCfg;
@@ -244,20 +254,17 @@ fn read_local_inputs(
     input_map: Res<BaseInputMap>,
     gc_ports: Res<gamecube::GcPorts>,
     gamepads: Query<&Gamepad>,
-    assignments: Res<LocalInputAssignments>,
+    assignments: Res<MatchInputAssignments>,
     local_players: Res<LocalPlayers>,
     game_settings: Res<GameSettings>,
 ) {
     let mut local_inputs = HashMap::new();
 
     for handle in &local_players.0 {
-        let assigned = assignments
+        let assigned = assignments.get_for_handle(*handle);
-            .0
-            .iter()
-            .find(|(player_handle, _)| player_handle == handle);
         let gamepad = match assigned {
-            Some((_, LocalInputSource::Gamepad(entity))) => gamepads.get(*entity).ok(),
+            Some(LocalInputSource::Gamepad(entity)) => gamepads.get(entity).ok(),
-            Some((_, LocalInputSource::Keyboard)) => None,
+            Some(LocalInputSource::Keyboard) => None,
             None => gc_ports
                 .entities
                 .get(*handle)
@@ -267,8 +274,8 @@ fn read_local_inputs(
         };
 
         let mut input_frame = match assigned {
-            Some((_, LocalInputSource::Keyboard)) => keyboard::sample_keyboard(&key, &input_map),
+            Some(LocalInputSource::Keyboard) => keyboard::sample_keyboard(&key, &input_map),
-            Some((_, LocalInputSource::Gamepad(_))) => gamepad
+            Some(LocalInputSource::Gamepad(_)) => gamepad
                 .map(|pad| gamepad::sample_gamepad(pad, &input_map))
                 .unwrap_or_default(),
             None => FighterInputFrame::default(),

src/match_loading.rs

@@ -19,9 +19,8 @@ use crate::{
         spawn_fighter,
         visual::FighterAnimations,
     },
-    input::{LocalInputAssignments, LocalInputSource},
+    input::{LocalInputAssignments, LocalInputSource, MatchInputAssignments},
     match_runtime::MatchState,
-    math::{int::FGi32, vec::FGVec2},
     netcode::{
         GGRSCfg,
         session::{ConnectionStatus, SessionConfig, create_session},
@@ -35,7 +34,10 @@ use crate::{
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
 pub struct MatchPlayer {
+    /// Dense index used by GGRS and rollback-simulated player state.
     pub handle: usize,
+    /// Physical controller port selected in the menu.
+    pub controller_port: usize,
     pub fighter: FighterId,
 }
 
@@ -46,6 +48,22 @@ pub struct MatchConfig {
     pub rules: MatchRules,
 }
 
+impl MatchConfig {
+    /// Maps a GGRS handle to the controller port used by gameplay.
+    ///
+    /// Multiplayer uses the stable, dense GGRS handle as the port. A
+    /// single-player match preserves the physical controller port selected in
+    /// the menu (for example, port 3 remains port 3).
+    pub fn controller_port_for_handle(&self, handle: usize) -> Option<usize> {
+        let player = self.players.iter().find(|player| player.handle == handle)?;
+        Some(if self.players.len() > 1 {
+            handle
+        } else {
+            player.controller_port
+        })
+    }
+}
+
 #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
 pub enum MatchRules {
     Stock {
@@ -228,6 +246,7 @@ pub fn initiate_default_match(
     let players = (0..args.players)
         .map(|handle| MatchPlayer {
             handle,
+            controller_port: handle,
             fighter: FighterId::TestFighter,
         })
         .collect();
@@ -263,6 +282,7 @@ pub fn initiate_default_match(
 pub fn prepare_match(
     mut commands: Commands,
     config: Res<MatchConfig>,
+    input_assignments: Res<LocalInputAssignments>,
     assets: Res<MatchAssets>,
     gltfs: Res<Assets<Gltf>>,
     baked_animations: Res<Assets<BakedFighterAnimations>>,
@@ -277,7 +297,7 @@ pub fn prepare_match(
     if !valid_player_handles(&config.players) {
         fail_match(
             &mut next_state,
-            "player handles must be unique and cover 0..player_count",
+            "player handles must be dense, unique, and non-empty",
         );
         return;
     }
@@ -287,6 +307,20 @@ pub fn prepare_match(
         return;
     }
 
+    let stage_handle = stage_registry
+        .get(config.stage)
+        .expect("Initialization check should ensure all stages exist");
+    let stage_manifest = stage_manifests
+        .get(&stage_handle)
+        .expect("Initialization check should ensure stage manifests are kept alive");
+    let spawn_positions = match stage_manifest.neutral_spawn_positions(config.players.len()) {
+        Ok(positions) => positions,
+        Err(error) => {
+            fail_match(&mut next_state, &error);
+            return;
+        }
+    };
+
     if assets.fighters.len() != config.players.len() {
         fail_match(
             &mut next_state,
@@ -449,7 +483,8 @@ pub fn prepare_match(
         ));
     }
 
-    let session_config = match SessionConfig::from_args(&args, config.players.len()) {
+    let session_player_count = player_count_for_handles(&config.players);
+    let session_config = match SessionConfig::from_args(&args, session_player_count) {
         Ok(config) => config,
         Err(error) => {
             fail_match(
@@ -459,7 +494,7 @@ pub fn prepare_match(
             return;
         }
     };
-    let session = match create_session(&args, config.players.len()) {
+    let session = match create_session(&args, session_player_count) {
         Ok(session) => session,
         Err(error) => {
             fail_match(
@@ -470,14 +505,13 @@ pub fn prepare_match(
         }
     };
 
+    commands.insert_resource(create_match_input_assignments(
+        &input_assignments,
+        &config.players,
+    ));
+
     let root = commands.spawn((Name::new("Match"), MatchRoot)).id();
 
-    let stage_handle = stage_registry
-        .get(config.stage)
-        .expect("Initialization check should ensure all stages exist");
-    let stage_manifest = stage_manifests
-        .get(&stage_handle)
-        .expect("Initialization check should ensure stage manifests are kept alive");
     stage::spawn_stage(
         &mut commands,
         root,
@@ -487,14 +521,18 @@ pub fn prepare_match(
     );
 
     let mut fighter_roster = Vec::with_capacity(config.players.len());
-    for (index, (player, (scene, animations, attack_scripts, manifest_handle, model_scale, ecb_bone_indices))) in
+
+    for (spawn_index, (player, (scene, animations, attack_scripts, manifest_handle, model_scale, ecb_bone_indices))) in
         config.players.iter().zip(prepared).enumerate()
     {
-        let spawn_x = (index as i32 * 2 + 1 - config.players.len() as i32) * 5;
+        let spawn_point = spawn_positions[spawn_index];
         fighter_roster.push(spawn_fighter(
             &mut commands,
             player.handle,
-            FGVec2::new(FGi32::from_num(spawn_x), FGi32::lit("12.5")),
+            config
+                .controller_port_for_handle(player.handle)
+                .expect("validated match config contains every player handle"),
+            spawn_point,
             manifest_handle.clone(),
             model_scale,
             animations,
@@ -518,12 +556,30 @@ fn fail_match(next_state: &mut NextState<AppState>, message: &str) {
 }
 
 fn valid_player_handles(players: &[MatchPlayer]) -> bool {
-    let mut handles = players
+    if players.is_empty() {
-        .iter()
+        return false;
-        .map(|player| player.handle)
+    }
-        .collect::<Vec<_>>();
+
+    let mut handles = players.iter().map(|player| player.handle).collect::<Vec<_>>();
     handles.sort_unstable();
-    handles == (0..players.len()).collect::<Vec<_>>()
+    handles.into_iter().eq(0..players.len())
+}
+
+fn player_count_for_handles(players: &[MatchPlayer]) -> usize {
+    players.len()
+}
+
+fn create_match_input_assignments(
+    assignments: &LocalInputAssignments,
+    players: &[MatchPlayer],
+) -> MatchInputAssignments {
+    let mut match_assignments = vec![None; players.len()];
+    for player in players {
+        match_assignments[player.handle] = assignments
+            .get_from_slot(player.controller_port)
+            .copied();
+    }
+    MatchInputAssignments(match_assignments)
 }
 
 pub fn cleanup_match(
@@ -544,6 +600,7 @@ pub fn cleanup_match(
     commands.remove_resource::<MatchAssets>();
     commands.remove_resource::<MatchConfig>();
     commands.remove_resource::<MatchState>();
+    commands.remove_resource::<MatchInputAssignments>();
     commands.remove_resource::<FighterRoster>();
 }
 
@@ -558,10 +615,12 @@ mod tests {
             players: vec![
                 MatchPlayer {
                     handle: 0,
+                    controller_port: 0,
                     fighter: FighterId::TestFighter,
                 },
                 MatchPlayer {
                     handle: 1,
+                    controller_port: 1,
                     fighter: FighterId::TestFighter,
                 },
             ],
@@ -579,10 +638,12 @@ mod tests {
         let players = [
             MatchPlayer {
                 handle: 0,
+                controller_port: 0,
                 fighter: FighterId::TestFighter,
             },
             MatchPlayer {
                 handle: 0,
+                controller_port: 1,
                 fighter: FighterId::TestFighter,
             },
         ];
@@ -590,6 +651,88 @@ mod tests {
         assert!(!valid_player_handles(&players));
     }
 
+    #[test]
+    fn player_handles_must_not_have_gaps() {
+        let players = [
+            MatchPlayer {
+                handle: 0,
+                controller_port: 0,
+                fighter: FighterId::TestFighter,
+            },
+            MatchPlayer {
+                handle: 2,
+                controller_port: 3,
+                fighter: FighterId::TestFighter,
+            },
+        ];
+
+        assert!(!valid_player_handles(&players));
+        assert_eq!(player_count_for_handles(&players), 2);
+    }
+
+    #[test]
+    fn controller_ports_use_ggrs_handles_only_in_multiplayer() {
+        let single_player = MatchConfig {
+            stage: StageId::TestStage,
+            players: vec![MatchPlayer {
+                handle: 0,
+                controller_port: 3,
+                fighter: FighterId::TestFighter,
+            }],
+            rules: MatchRules::default(),
+        };
+        assert_eq!(single_player.controller_port_for_handle(0), Some(3));
+
+        let multiplayer = MatchConfig {
+            stage: StageId::TestStage,
+            players: vec![
+                MatchPlayer {
+                    handle: 0,
+                    controller_port: 0,
+                    fighter: FighterId::TestFighter,
+                },
+                MatchPlayer {
+                    handle: 1,
+                    controller_port: 3,
+                    fighter: FighterId::TestFighter,
+                },
+            ],
+            rules: MatchRules::default(),
+        };
+        assert_eq!(multiplayer.controller_port_for_handle(0), Some(0));
+        assert_eq!(multiplayer.controller_port_for_handle(1), Some(1));
+    }
+
+    #[test]
+    fn match_input_assignments_map_ports_to_ggrs_handles_without_mutating_ports() {
+        let players = [
+            MatchPlayer {
+                handle: 0,
+                controller_port: 0,
+                fighter: FighterId::TestFighter,
+            },
+            MatchPlayer {
+                handle: 1,
+                controller_port: 3,
+                fighter: FighterId::TestFighter,
+            },
+        ];
+        let assignments = LocalInputAssignments(vec![
+            (0, LocalInputSource::Keyboard),
+            (3, LocalInputSource::Gamepad(Entity::PLACEHOLDER)),
+        ]);
+
+        let match_assignments = create_match_input_assignments(&assignments, &players);
+
+        assert_eq!(match_assignments.get_for_handle(0), Some(LocalInputSource::Keyboard));
+        assert_eq!(
+            match_assignments.get_for_handle(1),
+            Some(LocalInputSource::Gamepad(Entity::PLACEHOLDER))
+        );
+        assert_eq!(assignments[0].0, 0);
+        assert_eq!(assignments[1].0, 3);
+    }
+
     #[test]
     fn match_rules_reject_zero_limits() {
         assert!(

src/match_runtime.rs

@@ -117,10 +117,12 @@ mod tests {
             players: vec![
                 MatchPlayer {
                     handle: 1,
+                    controller_port: 3,
                     fighter: FighterId::TestFighter,
                 },
                 MatchPlayer {
                     handle: 0,
+                    controller_port: 0,
                     fighter: FighterId::TestFighter,
                 },
             ],

src/menus/match_config.rs

@@ -65,7 +65,10 @@ impl MenuMatchConfig {
 
         let stage = self.stage.ok_or(MenuMatchConfigErrors::StageNotSelected)?;
 
-        for player in self.players.iter() {
+        let mut players = self.players.iter().collect::<Vec<_>>();
+        players.sort_unstable_by_key(|player| player.slot);
+
+        for (handle, player) in players.into_iter().enumerate() {
             let fighter_id =
                 player
                     .fighter
@@ -74,7 +77,8 @@ impl MenuMatchConfig {
                     ))?;
             match_players.push(MatchPlayer {
                 fighter: fighter_id,
-                handle: player.slot,
+                handle,
+                controller_port: player.slot,
             });
         }
 
@@ -102,4 +106,27 @@ mod tests {
 
         assert_eq!(menu.to_match_config().unwrap().rules, MatchRules::default());
     }
+
+    #[test]
+    fn sparse_controller_ports_get_dense_ggrs_handles() {
+        let menu = MenuMatchConfig {
+            stage: Some(StageId::TestStage),
+            players: vec![
+                MenuMatchPlayerSlot {
+                    slot: 3,
+                    fighter: Some(FighterId::TestFighter),
+                },
+                MenuMatchPlayerSlot {
+                    slot: 0,
+                    fighter: Some(FighterId::TestFighter),
+                },
+            ],
+        };
+
+        let config = menu.to_match_config().unwrap();
+        assert_eq!(config.players[0].handle, 0);
+        assert_eq!(config.players[0].controller_port, 0);
+        assert_eq!(config.players[1].handle, 1);
+        assert_eq!(config.players[1].controller_port, 3);
+    }
 }

src/player.rs

@@ -10,5 +10,8 @@ use bevy_ggrs::prelude::*;
 #[derive(Default, Component)]
 #[require(Rollback, Transform)]
 pub struct Player {
+    /// Dense GGRS session index.
     pub handle: usize,
+    /// Port used for port-dependent gameplay such as respawn placement.
+    pub controller_port: usize,
 }

src/replay.rs

@@ -17,7 +17,7 @@ use crate::{
 };
 
 const MAGIC: &[u8; 8] = b"SPRPLY01";
-pub const REPLAY_VERSION: u32 = 2;
+pub const REPLAY_VERSION: u32 = 3;
 
 #[derive(Clone, Copy, Debug, Default, Eq, PartialEq, ValueEnum)]
 pub enum ReplayFormat {
@@ -140,7 +140,7 @@ fn validate(replay: &Replay) -> Result<(), String> {
         ));
     }
     if replay.players_are_invalid() {
-        return Err("replay player handles must cover 0..player_count".into());
+        return Err("replay player handles must be unique".into());
     }
     if replay.frames.is_empty() {
         return Err("replay must contain at least one frame".into());
@@ -185,7 +185,7 @@ impl Replay {
             .map(|player| player.handle)
             .collect();
         handles.sort_unstable();
-        handles != (0..handles.len()).collect::<Vec<_>>()
+        handles.is_empty() || !handles.into_iter().eq(0..self.match_config.players.len())
     }
 
     fn frame(&self, frame: i32) -> Option<&ReplayFrame> {
@@ -374,6 +374,7 @@ mod tests {
                 stage: StageId::TestStage,
                 players: vec![MatchPlayer {
                     handle: 0,
+                    controller_port: 0,
                     fighter: FighterId::TestFighter,
                 }],
                 rules: MatchRules::Timed {

src/stage/debug.rs

@@ -1,6 +1,11 @@
 use bevy::{color::palettes::css::RED, prelude::*};
 
-use crate::stage::line::StageCollision;
+use crate::{
+    match_loading::MatchConfig, math::{int::FGi32, vec3::FGVec3}, stage::{
+        line::StageCollision,
+        manifest::{StageManifest, StageManifestRegistry},
+    },
+};
 
 pub fn debug_draw_scene(mut gizmos: Gizmos, stage_collision: Res<StageCollision>) {
     for poly in stage_collision.stage_polys.iter() {
@@ -16,3 +21,52 @@ pub fn debug_draw_scene(mut gizmos: Gizmos, stage_collision: Res<StageCollision>
         }
     }
 }
+
+pub fn debug_draw_blast_zones(
+    mut gizmos: Gizmos,
+    stage_registry: Res<StageManifestRegistry>,
+    stage_manifests: Res<Assets<StageManifest>>,
+    match_config: Res<MatchConfig>,
+) {
+    let Some(stage_manifest_handle) = stage_registry.get(match_config.stage) else {
+        return;
+    };
+
+    let Some(stage_manifest) = stage_manifests.get(&stage_manifest_handle) else {
+        return;
+    };
+
+    let top_left = stage_manifest.blast_zone_top_left.to_vec2();
+    let bottom_right = stage_manifest.blast_zone_bottom_right.to_vec2();
+    let center = (top_left + bottom_right) / 2.0;
+    let size = (bottom_right - top_left).abs();
+
+    gizmos.rect(
+        Vec3::new(center.x, center.y, 0.0),
+        size,
+        bevy::color::palettes::css::BLUE,
+    );
+}
+
+pub fn debug_draw_spawn_positions(
+    mut gizmos: Gizmos,
+    stage_registry: Res<StageManifestRegistry>,
+    stage_manifests: Res<Assets<StageManifest>>,
+    match_config: Res<MatchConfig>,
+) {
+    let Some(stage_manifest_handle) = stage_registry.get(match_config.stage) else {
+        return;
+    };
+
+    let Some(stage_manifest) = stage_manifests.get(&stage_manifest_handle) else {
+        return;
+    };
+
+    for spawn_point in stage_manifest.spawn_points.iter() {
+        gizmos.cross(FGVec3::new(spawn_point.x, spawn_point.y, FGi32::ZERO).to_vec3(), 2.0, bevy::color::palettes::css::BLUE);
+    }
+
+    for respawn_point in stage_manifest.respawn_points.iter() {
+        gizmos.cross(FGVec3::new(respawn_point.x, respawn_point.y, FGi32::ZERO).to_vec3(), 2.0, bevy::color::palettes::css::HOT_PINK);
+    }
+}

src/stage/manifest.rs

@@ -1,4 +1,4 @@
-use std::collections::HashMap;
+use std::collections::{HashMap, HashSet};
 
 use bevy_asset_loader::asset_collection::AssetCollection;
 use ron_asset_manager::prelude::RonAsset;
@@ -7,14 +7,10 @@ use strum::IntoEnumIterator;
 use strum_macros::EnumIter;
 
 use crate::{
-    AppState,
+    AppState, game_settings::GameSettings, math::{vec::FGVec2}, stage::{
-    game_settings::GameSettings,
-    math::vec::FGVec2,
-    stage::{
         StagePoly,
         line::{StageCollision, StagePolyLineSegmentType, StagePolyType},
-    },
+    }, texture_reference::TextureReference,
-    texture_reference::TextureReference,
 };
 use bevy::prelude::*;
 
@@ -87,6 +83,17 @@ pub struct StageManifest {
     pub icon: TextureReference,
     pub camera: StageCameraProfile,
     pub polygons: Vec<StagePolyDefinition>,
+
+    #[reflect(ignore)]
+    pub blast_zone_top_left: FGVec2,
+    #[reflect(ignore)]
+    pub blast_zone_bottom_right: FGVec2,
+
+    #[reflect(ignore)]
+    pub spawn_points: Vec<FGVec2>,
+    pub neutral_spawn_point_sets: Vec<Vec<usize>>,
+    #[reflect(ignore)]
+    pub respawn_points: Vec<FGVec2>,
 }
 
 #[derive(Resource)]
@@ -162,6 +169,13 @@ pub fn prepare_stage_manifests(
             );
             return;
         }
+        if let Err(error) = manifest.validate_spawn_points() {
+            fail(
+                &mut next_state,
+                &format!("{:?} has invalid spawn points: {error}", manifest.id),
+            );
+            return;
+        }
         if registry.insert(manifest.id, handle.clone()).is_some() {
             fail(
                 &mut next_state,
@@ -186,6 +200,73 @@ pub fn prepare_stage_manifests(
 }
 
 impl StageManifest {
+    pub fn neutral_spawn_positions(&self, player_count: usize) -> Result<Vec<FGVec2>, String> {
+        if player_count == 0 {
+            return Err("a match must contain at least one player".to_owned());
+        }
+
+        let layout = self
+            .neutral_spawn_point_sets
+            .get(player_count - 1)
+            .ok_or_else(|| format!("no spawn layout for {player_count} players"))?;
+
+        if layout.len() != player_count {
+            return Err(format!(
+                "the {player_count}-player layout contains {} positions",
+                layout.len()
+            ));
+        }
+
+        layout
+            .iter()
+            .map(|&index| {
+                self.spawn_points.get(index).copied().ok_or_else(|| {
+                    format!("the {player_count}-player layout references spawn point {index}")
+                })
+            })
+            .collect()
+    }
+
+    fn validate_spawn_points(&self) -> Result<(), String> {
+        if self.spawn_points.is_empty() {
+            return Err("no spawn points are configured".to_owned());
+        }
+
+        if self.respawn_points.is_empty() {
+            return Err("no respawn points are configured".to_owned());
+        }
+
+        if self.neutral_spawn_point_sets.is_empty() {
+            return Err("no neutral spawn layouts are configured".to_owned());
+        }
+
+        for (layout_index, layout) in self.neutral_spawn_point_sets.iter().enumerate() {
+            let player_count = layout_index + 1;
+            if layout.len() != player_count {
+                return Err(format!(
+                    "the {player_count}-player layout contains {} positions",
+                    layout.len()
+                ));
+            }
+
+            let mut unique_indices = HashSet::with_capacity(layout.len());
+            for &spawn_point_index in layout {
+                if spawn_point_index >= self.spawn_points.len() {
+                    return Err(format!(
+                        "the {player_count}-player layout references spawn point {spawn_point_index}"
+                    ));
+                }
+                if !unique_indices.insert(spawn_point_index) {
+                    return Err(format!(
+                        "the {player_count}-player layout uses spawn point {spawn_point_index} more than once"
+                    ));
+                }
+            }
+        }
+
+        Ok(())
+    }
+
     pub fn to_collision(&self) -> StageCollision {
         let stage_polys: Vec<StagePoly> = self
             .polygons

src/stage/mod.rs

@@ -10,7 +10,7 @@ pub mod scene;
 
 pub use line::{StagePlaneIntersectResult, StagePoly};
 
-use crate::stage::{line::StageCollision, manifest::StageCameraProfile};
+use crate::{match_loading::MatchConfig, stage::{line::StageCollision, manifest::StageCameraProfile}};
 
 /// Owns the stage geometry: which scene gets spawned and how it is drawn.
 #[derive(Default)]
@@ -20,9 +20,17 @@ impl Plugin for StagePlugin {
     fn build(&self, app: &mut App) {
         app.add_systems(
             Update,
-            debug::debug_draw_scene
+            (
+                (debug::debug_draw_scene
                     .run_if(resource_exists::<line::StageCollision>)
-                .run_if(crate::debug_tools::stage_collision_enabled),
+                    .run_if(crate::debug_tools::stage_collision_enabled)),
+                (debug::debug_draw_blast_zones
+                    .run_if(resource_exists::<MatchConfig>)
+                    .run_if(crate::debug_tools::blast_zones_enabled),),
+                (debug::debug_draw_spawn_positions
+                    .run_if(resource_exists::<MatchConfig>)
+                    .run_if(crate::debug_tools::spawn_positions_enabled),),
+            ),
         );
     }
 }