refactor to plugin

src/snake/main.rs

@@ -30,6 +30,9 @@ impl Size {
     }
 }
 
+#[derive(Resource)]
+struct MovementTimer(Timer);
+
 fn snake_movement_system(
     input: Res<ButtonInput<KeyCode>>,
 
@@ -100,8 +103,21 @@ fn setup_camera(mut commands: Commands) {
     commands.spawn((Camera2d {},));
 }
 
+pub struct SnakePlugin;
+impl Plugin for SnakePlugin {
+    fn build(&self, app: &mut App) {
+        app.add_systems(Startup, (setup_camera, setup_player));
+        app.add_systems(Update, snake_movement_system);
+        app.add_systems(PostUpdate, (scale_translation, position_translation));
+
+        app.insert_resource(MovementTimer(Timer::from_seconds(
+            1.0,
+            TimerMode::Repeating,
+        )));
+    }
+}
+
 fn main() {
-    let systems = snake_movement_system;
     App::new()
         .add_plugins(
             DefaultPlugins.set(WindowPlugin {
@@ -118,8 +134,6 @@ fn main() {
             }),
         )
         .add_plugins(WorldInspectorPlugin::new())
-        .add_systems(Startup, (setup_camera, setup_player))
-        .add_systems(Update, systems)
-        .add_systems(PostUpdate, (scale_translation, position_translation))
+        .add_plugins(SnakePlugin)
         .run();
 }