Fix: apply thrust input properly

Yay for funny coordinate spaces. I was, again, using the wrong
operations to get the 2D Cartesian angle and apply force to the ship.

src/asteroids.rs

@@ -1,12 +1,13 @@
+//! This is the module containing all the rock-related things.
+//! Not... not the whole game.
+
 use bevy_rapier2d::prelude::*;
 use rand::{Rng, SeedableRng};
 use std::time::Duration;
 
-/// This is the module containing all the rock-related things
-/// not... not the whole game.
 use bevy::prelude::*;
 
-use crate::{GameAssets, Position, Rotation, Velocity, WorldSize};
+use crate::{GameAssets, WorldSize, physics::Velocity};
 
 #[derive(Component, Deref, DerefMut)]
 pub struct Asteroid(AsteroidSize);
@@ -119,9 +120,8 @@ pub fn spawn_asteroid(
             Asteroid(AsteroidSize::Small),
             Collider::ball(collider_radius),
             Sensor,
-            Position(spawn.pos),
+            Transform::from_translation(spawn.pos.extend(0.0)),
             Velocity(spawn.vel),
-            Rotation(0.0),
             Mesh2d(mesh),
             MeshMaterial2d(material),
         ));

src/config.rs

@@ -1,7 +1,5 @@
-/*
- Global constants used all over the program. Rather than leaving them scattered
-where ever they happen to be needed, I'm concentrating them here.
-*/
+//! Global constants used all over the program. Rather than leaving them scattered
+//! where ever they happen to be needed, I'm concentrating them here.
 
 use bevy::color::Color;
 
@@ -15,6 +13,6 @@ pub(crate) const ASTEROID_SMALL_COLOR: Color = Color::srgb(1.0, 0., 0.);
 // TODO: asteroid medium & large
 
 pub(crate) const SHIP_THRUST: f32 = 1.0;
-pub(crate) const SHIP_ROTATION: f32 = 0.1; // +/- rotation speed in... radians per frame
+pub(crate) const SHIP_ROTATION: f32 = 4.0; // +/- rotation speed in... radians per frame
 
 pub const RNG_SEED: [u8; 32] = *b"12345678909876543210123456789098";

src/lib.rs

@@ -1,24 +1,27 @@
 mod asteroids;
 pub mod config;
 mod event;
+mod physics;
 mod preparation_widget;
 mod ship;
 mod title_screen;
 
-use crate::config::{BACKGROUND_COLOR, PLAYER_SHIP_COLOR, SHIP_ROTATION, SHIP_THRUST, WINDOW_SIZE};
+use crate::asteroids::{Asteroid, AsteroidSpawner};
+use crate::config::{
+    ASTEROID_SMALL_COLOR, BACKGROUND_COLOR, PLAYER_SHIP_COLOR, SHIP_ROTATION, SHIP_THRUST,
+    SHIP_THRUSTER_COLOR_ACTIVE, SHIP_THRUSTER_COLOR_INACTIVE, WINDOW_SIZE,
+};
+use crate::physics::AngularVelocity;
+use crate::ship::Ship;
 
-use asteroids::{Asteroid, AsteroidSpawner};
 use bevy::prelude::*;
 use bevy_inspector_egui::InspectorOptions;
 use bevy_inspector_egui::prelude::ReflectInspectorOptions;
-
 use bevy_rapier2d::{
     plugin::{NoUserData, RapierPhysicsPlugin},
     prelude::*,
     render::RapierDebugRenderPlugin,
 };
-use config::{ASTEROID_SMALL_COLOR, SHIP_THRUSTER_COLOR_ACTIVE, SHIP_THRUSTER_COLOR_INACTIVE};
-use ship::Ship;
 
 pub struct AsteroidPlugin;
 
@@ -47,7 +50,7 @@ impl Plugin for AsteroidPlugin {
             (
                 input_ship_thruster,
                 input_ship_rotation,
-                wrap_entities,
+                physics::wrap_entities,
                 asteroids::tick_asteroid_manager,
                 asteroids::spawn_asteroid.after(asteroids::tick_asteroid_manager),
                 collision_listener,
@@ -58,13 +61,16 @@ impl Plugin for AsteroidPlugin {
         )
         .add_systems(
             FixedPostUpdate,
-            (integrate_velocity, update_positions, apply_rotation_to_mesh)
+            (
+                physics::integrate_velocity,
+                physics::integrate_angular_velocity,
+            )
                 .run_if(in_state(GameState::Playing)),
         )
         .add_event::<asteroids::SpawnAsteroid>()
         .add_event::<event::AsteroidDestroy>()
         .add_event::<event::ShipDestroy>();
-        app.insert_state(GameState::TitleScreen);
+        app.insert_state(GameState::Playing);
     }
 }
 
@@ -130,19 +136,6 @@ pub enum GameState {
     GameOver,    // Game has ended. Present game over dialogue and await user restart
 }
 
-#[derive(Component)]
-struct Position(bevy::math::Vec2);
-
-#[derive(Component)]
-struct Velocity(bevy::math::Vec2);
-
-#[derive(Component)]
-struct Rotation(f32);
-
-/// Marker for any entity that should wrap on screen edges
-#[derive(Component)]
-struct Wrapping;
-
 #[derive(Resource, Debug, Deref, Clone, Copy)]
 struct Score(i32);
 
@@ -244,14 +237,14 @@ fn spawn_camera(mut commands: Commands) {
 */
 fn input_ship_thruster(
     keyboard_input: Res<ButtonInput<KeyCode>>,
-    mut query: Query<(&mut Velocity, &Rotation, &mut Children), With<Ship>>,
+    mut query: Query<(&mut physics::Velocity, &Transform, &mut Children), With<Ship>>,
     mut commands: Commands,
     game_assets: Res<GameAssets>,
 ) {
     // TODO: Maybe change for a Single<Ship>> so this only runs for the one ship
     // buuut... that would silently do nothing if there are 0 or >1 ships, and
     // I might want to crash on purpose in that case.
-    let Ok((mut velocity, rotation, children)) = query.single_mut() else {
+    let Ok((mut velocity, transform, children)) = query.single_mut() else {
         let count = query.iter().count();
         panic!("There should be exactly one player ship! Instead, there seems to be {count}.");
     };
@@ -261,7 +254,7 @@ fn input_ship_thruster(
         .expect("Couldn't find first child, which should be the thruster");
 
     if keyboard_input.pressed(KeyCode::KeyW) {
-        velocity.0 += Vec2::from_angle(rotation.0) * SHIP_THRUST;
+        velocity.0 += (transform.rotation * Vec3::X).xy() * SHIP_THRUST;
         commands
             .entity(*thrusters)
             .insert(MeshMaterial2d(game_assets.thruster_mat_active()));
@@ -278,67 +271,19 @@ fn input_ship_thruster(
 */
 fn input_ship_rotation(
     keyboard_input: Res<ButtonInput<KeyCode>>,
-    mut query: Query<&mut Rotation, With<Ship>>,
+    mut query: Query<&mut AngularVelocity, With<Ship>>,
 ) {
-    let Ok(mut rotation) = query.single_mut() else {
+    let Ok(mut angular_vel) = query.single_mut() else {
         let count = query.iter().count();
         panic!("There should be exactly one player ship! Instead, there seems to be {count}.");
     };
 
     if keyboard_input.pressed(KeyCode::KeyA) {
-        rotation.0 += SHIP_ROTATION;
+        angular_vel.0 = SHIP_ROTATION;
     } else if keyboard_input.pressed(KeyCode::KeyD) {
-        rotation.0 -= SHIP_ROTATION;
-    }
-}
-
-// TODO: Combine movement integration steps into one function
-// They need to be ordered so the physics is deterministic. Bevy can enforce
-// order, but it makes more sense to cut out the extra machinery and have one
-// single function. Probably better for cache locality or whatever, too.
-/*
- Add velocity to position
-*/
-fn integrate_velocity(mut query: Query<(&mut Position, &Velocity)>, time: Res<Time>) {
-    for (mut position, velocity) in &mut query {
-        position.0 += velocity.0 * time.delta_secs();
-    }
-}
-
-fn update_positions(mut query: Query<(&mut Transform, &Position)>) {
-    for (mut transform, position) in &mut query {
-        transform.translation.x = position.0.x;
-        transform.translation.y = position.0.y;
-    }
-}
-
-/*
- Assigns the rotation to the transform by copying it from the Rotation component.
-*/
-fn apply_rotation_to_mesh(mut query: Query<(&mut Transform, &Rotation)>) {
-    for (mut transform, rotation) in &mut query {
-        transform.rotation = Quat::from_rotation_z(rotation.0);
-    }
-}
-
-fn wrap_entities(mut query: Query<&mut Position, With<Wrapping>>, world_size: Res<WorldSize>) {
-    let right = world_size.width / 2.0;
-    let left = -right;
-    let top = world_size.height / 2.0;
-    let bottom = -top;
-
-    for mut pos in query.iter_mut() {
-        if pos.0.x > right {
-            pos.0.x = left;
-        } else if pos.0.x < left {
-            pos.0.x = right;
-        }
-
-        if pos.0.y > top {
-            pos.0.y = bottom;
-        } else if pos.0.y < bottom {
-            pos.0.y = top;
-        }
+        angular_vel.0 = -SHIP_ROTATION;
+    } else {
+        angular_vel.0 = 0.0;
     }
 }
 

src/physics.rs

@@ -0,0 +1,59 @@
+//! Custom physics items
+//! TODO: Refactor in terms of Rapier2D, *or* implement colliders and remove it.
+
+use crate::WorldSize;
+
+use bevy::prelude::*;
+
+#[derive(Component)]
+pub(crate) struct Velocity(pub(crate) bevy::math::Vec2);
+
+#[derive(Component)]
+pub(crate) struct AngularVelocity(pub(crate) f32);
+
+/// Marker for any entity that should wrap on screen edges
+#[derive(Component)]
+pub(crate) struct Wrapping;
+
+/// Integrate linear velocity and update the entity's transform.
+pub(crate) fn integrate_velocity(mut query: Query<(&mut Transform, &Velocity)>, time: Res<Time>) {
+    for (mut transform, velocity) in &mut query {
+        let delta = velocity.0 * time.delta_secs();
+        transform.translation += delta.extend(0.0);
+    }
+}
+
+/// Integrate angular velocity and update the entity's transform.
+pub(crate) fn integrate_angular_velocity(
+    mut objects: Query<(&mut Transform, &AngularVelocity)>,
+    time: Res<Time>,
+) {
+    for (mut transform, ang_vel) in &mut objects {
+        let delta = ang_vel.0 * time.delta_secs();
+        transform.rotate_z(delta);
+    }
+}
+
+pub(crate) fn wrap_entities(
+    mut query: Query<&mut Transform, With<Wrapping>>,
+    world_size: Res<WorldSize>,
+) {
+    let right = world_size.width / 2.0;
+    let left = -right;
+    let top = world_size.height / 2.0;
+    let bottom = -top;
+
+    for mut pos in query.iter_mut() {
+        if pos.translation.x > right {
+            pos.translation.x = left;
+        } else if pos.translation.x < left {
+            pos.translation.x = right;
+        }
+
+        if pos.translation.y > top {
+            pos.translation.y = bottom;
+        } else if pos.translation.y < bottom {
+            pos.translation.y = top;
+        }
+    }
+}

src/preparation_widget.rs

@@ -1,10 +1,10 @@
+use crate::GameState;
+
 use bevy::{
     color::palettes::css::{BLACK, GREEN, LIGHT_BLUE, RED},
     prelude::*,
 };
 
-use crate::GameState;
-
 pub fn preparation_widget_plugin(app: &mut App) {
     app.add_systems(OnEnter(GameState::GetReady), spawn_get_ready)
         .add_systems(OnExit(GameState::GetReady), despawn_get_ready)

src/ship.rs

@@ -1,8 +1,11 @@
+use crate::{
+    AngularVelocity, GameAssets,
+    physics::{Velocity, Wrapping},
+};
+
 use bevy::prelude::*;
 use bevy_rapier2d::prelude::*;
 
-use crate::{GameAssets, Position, Rotation, Velocity, Wrapping};
-
 #[derive(Component)]
 pub struct Ship;
 
@@ -15,9 +18,8 @@ pub fn spawn_player(mut commands: Commands, game_assets: Res<GameAssets>) {
             ActiveCollisionTypes::STATIC_STATIC,
             Ship,
             Wrapping,
-            Position(Vec2::default()),
             Velocity(Vec2::ZERO),
-            Rotation(0.0),
+            AngularVelocity(0.0),
             Mesh2d(game_assets.ship().0),
             MeshMaterial2d(game_assets.ship().1),
             Transform::default().with_scale(Vec3::new(20.0, 20.0, 20.0)),