From ef190538ff268319f53b7501e451e450d9701534 Mon Sep 17 00:00:00 2001
From: Elijah Voigt <elijah.caine.mv@gmail.com>
Date: Mon, 28 Jul 2025 20:12:56 -0700
Subject: [PATCH] Preserve velocities

---
 src/bin/flappy/main.rs | 21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/src/bin/flappy/main.rs b/src/bin/flappy/main.rs
index affcc82..566a2e6 100644
--- a/src/bin/flappy/main.rs
+++ b/src/bin/flappy/main.rs
@@ -94,6 +94,8 @@ enum PlayerState {
 struct Tape {
     translations: Vec<Vec3>,
     rotations: Vec<Quat>,
+    linear_velocities: Vec<LinearVelocity>,
+    angular_velocities: Vec<AngularVelocity>,
 }
 
 fn init_bird(
@@ -119,7 +121,6 @@ fn init_bird(
         RigidBody::Static,
         Collider::capsule(1.0, 1.0),
         Mass(1.0),
-        ExternalForce::new(Vec3::X * 1.0).with_persistence(true),
         ExternalImpulse::default().with_persistence(false),
         LockedAxes::ROTATION_LOCKED.lock_translation_z(),
     );
@@ -271,7 +272,7 @@ fn flap(
     );
 
     bird.iter_mut().for_each(|(t, mut f)| {
-        f.apply_impulse(t.rotation * Vec3::NEG_Z * 5.0);
+        f.apply_impulse(t.rotation * Vec3::NEG_Z * 5.0 + t.rotation * Vec3::X);
     });
 }
 
@@ -292,35 +293,43 @@ fn toggle_rewind(keycode: Res<ButtonInput<KeyCode>>, mut next: ResMut<NextState<
 
 fn record(
     #[cfg(debug_assertions)] state: Res<State<PlayerState>>,
-    mut birds: Query<(&Transform, &mut Tape), With<Bird>>,
+    mut birds: Query<(&Transform, &LinearVelocity, &AngularVelocity, &mut Tape), With<Bird>>,
 ) {
     debug_assert!(
         matches!(state.get(), PlayerState::Alive),
         "Only record in the alive state"
     );
 
-    birds.iter_mut().for_each(|(transform, mut tape)| {
+    birds.iter_mut().for_each(|(transform, linear_velocity, angular_velocity, mut tape)| {
         tape.translations.push(transform.translation);
         tape.rotations.push(transform.rotation);
+        tape.linear_velocities.push(*linear_velocity);
+        tape.angular_velocities.push(*angular_velocity);
     });
 }
 
 fn rewind(
     #[cfg(debug_assertions)] state: Res<State<PlayerState>>,
-    mut birds: Query<(&mut Transform, &mut Tape), With<Bird>>,
+    mut birds: Query<(&mut Transform, &mut AngularVelocity, &mut LinearVelocity, &mut Tape), With<Bird>>,
 ) {
     debug_assert!(
         matches!(state.get(), PlayerState::Rewind),
         "Only rewind in the rewinding state"
     );
 
-    birds.iter_mut().for_each(|(mut transform, mut tape)| {
+    birds.iter_mut().for_each(|(mut transform, mut angular_velocity, mut linear_velocity, mut tape)| {
         if let Some(t) = tape.translations.pop() {
             transform.translation = t;
         }
         if let Some(r) = tape.rotations.pop() {
             transform.rotation = r;
         }
+        if let Some(av) = tape.angular_velocities.pop() {
+            *angular_velocity = av;
+        }
+        if let Some(lv) = tape.linear_velocities.pop() {
+            *linear_velocity = lv;
+        }
     });
 }