Initial work on rollback and refactor

src/fighter/collision.rs

@@ -0,0 +1,31 @@
+//! Resolving an integrated fighter position against the stage.
+
+use bevy::{color::palettes::css::HOT_PINK, prelude::*};
+
+use crate::fighter::{FighterECB, FighterTranslation, FighterVelocity};
+use crate::stage::StageLine;
+
+pub fn collide_fighter_with_scene(
+    fighters: Query<(&FighterECB, &mut FighterVelocity, &mut FighterTranslation)>,
+    stage_planes: Query<&StageLine>,
+    mut gizmos: Gizmos,
+) {
+    for (ecb, mut velocity, mut translation) in fighters {
+        for plane in stage_planes {
+            let ray_from = translation.0;
+            let ray_to = translation.0 + Vec2::new(0.0, -ecb.vertical_half);
+
+            let intersection_result = plane.intersect_ray(Segment2d::new(ray_from, ray_to));
+
+            if let Some(result) = intersection_result {
+                gizmos.sphere(
+                    Isometry3d::from(Vec3::new(result.position.x, result.position.y, 0.0)),
+                    0.1f32,
+                    HOT_PINK,
+                );
+                velocity.0 = plane.project(velocity.0);
+                translation.0 = result.position + Vec2::new(0.0, ecb.vertical_half);
+            }
+        }
+    }
+}