backpack implementation (#15)

src/main.rs

@@ -1,5 +1,6 @@
 mod aim;
 mod alien;
+mod backpack;
 mod billboards;
 mod camera;
 mod cash;
@@ -94,6 +95,7 @@ fn main() {
     app.add_plugins(controls::plugin);
     app.add_plugins(sounds::plugin);
     app.add_plugins(camera::plugin);
+    app.add_plugins(backpack::plugin);
 
     app.insert_resource(AmbientLight {
         color: Color::WHITE,
@@ -104,10 +106,7 @@ fn main() {
 
     app.add_systems(Startup, (write_trenchbroom_config, music));
     app.add_systems(PostStartup, setup_scene);
-    app.add_systems(
-        Update,
-        (set_materials_unlit, set_tonemapping, set_shadows, spawn_box),
-    );
+    app.add_systems(Update, (set_materials_unlit, set_tonemapping, set_shadows));
 
     app.run();
 }
@@ -137,24 +136,6 @@ fn setup_scene(mut commands: Commands, asset_server: Res<AssetServer>) {
     ));
 }
 
-fn spawn_box(
-    mut commands: Commands,
-    mut meshes: ResMut<Assets<Mesh>>,
-    mut materials: ResMut<Assets<StandardMaterial>>,
-    keys: Res<ButtonInput<KeyCode>>,
-) {
-    if keys.just_pressed(KeyCode::Enter) {
-        commands.spawn((
-            RigidBody::Dynamic,
-            Collider::cuboid(5.0, 5.0, 5.0),
-            AngularVelocity(Vec3::new(2.5, 3.5, 1.5)),
-            Mesh3d(meshes.add(Cuboid::from_length(5.0))),
-            MeshMaterial3d(materials.add(Color::srgb_u8(124, 144, 255))),
-            Transform::from_xyz(0.0, 50.0, 0.0),
-        ));
-    }
-}
-
 fn music(asset_server: Res<AssetServer>, mut commands: Commands) {
     commands.spawn((
         AudioPlayer::new(asset_server.load("sfx/music/02.ogg")),