use gamestates and assetloader

src/shooting.rs

@@ -1,4 +1,5 @@
 use crate::{
+    GameState,
     aim::AimState,
     billboards::Billboard,
     npc::Hit,
@@ -39,10 +40,11 @@ struct ShotAssets {
 struct AnimationTimer(Timer);
 
 pub fn plugin(app: &mut App) {
-    app.add_systems(Startup, setup);
+    app.add_systems(OnEnter(GameState::Playing), setup);
     app.add_systems(
         Update,
-        (update, shot_collision, enemy_hit, timeout, animate_sprite),
+        (update, shot_collision, enemy_hit, timeout, animate_sprite)
+            .run_if(in_state(GameState::Playing)),
     );
     app.add_observer(on_trigger_state);
 }
@@ -52,6 +54,7 @@ fn setup(
     asset_server: Res<AssetServer>,
     mut sprite_params: Sprite3dParams,
 ) {
+    // TODO: use asset server
     let image = asset_server.load("textures/fx/impact.png");
     let layout = TextureAtlasLayout::from_grid(UVec2::splat(256), 7, 6, None, None);
     let texture_atlas_layout = sprite_params.atlas_layouts.add(layout);