fix flow a little bit

src/main.rs

@@ -13,7 +13,6 @@ mod main_menu;
 
 fn main() {
     App::new()
-        .init_state::<GameState>()
         .add_plugins((
             DefaultPlugins,
             asset_loading::plugin,
@@ -22,7 +21,8 @@ fn main() {
             level_instantiation::map_plugin,
             main_menu::plugin
         ))
-        .add_systems(Startup, setup)
+        .init_state::<GameState>()
+        .add_systems(OnEnter(GameState::Playing), setup)
         .run();
 }
 

src/main_menu.rs

@@ -8,7 +8,10 @@ struct OnMainMenuScreen;
 pub fn plugin(app: &mut App) {
     app
         .add_systems(OnEnter(GameState::Menu), setup_main_menu)
-        .add_systems(OnExit(GameState::Menu), despawn_screen::<OnMainMenuScreen>)
+        .add_systems(OnExit(GameState::Menu), (
+            remove_camera_2d,
+            despawn_screen::<OnMainMenuScreen>
+        ))
         .add_systems(Update, button_system.run_if(in_state(GameState::Menu)));
 }
 
@@ -30,6 +33,8 @@ const HOVERED_PRESSED_BUTTON: Color = Color::srgb(0.25, 0.65, 0.25);
 const PRESSED_BUTTON: Color = Color::srgb(0.35, 0.75, 0.35);
 
 fn setup_main_menu(mut commands: Commands) {
+    commands.spawn(Camera2d);
+
     let button_node = Node {
         width: Val::Px(300.0),
         height: Val::Px(65.0),
@@ -135,6 +140,12 @@ fn button_system(
     }
 }
 
+fn remove_camera_2d(mut commands: Commands, camera_query: Query<Entity, With<Camera2d>>) {
+    for camera in camera_query.iter() {
+        commands.entity(camera).despawn_recursive();
+    }
+}
+
 fn despawn_screen<T: Component>(to_despawn: Query<Entity, With<T>>, mut commands: Commands) {
     for entity in &to_despawn {
         commands.entity(entity).despawn_recursive();

src/player_plugin.rs

@@ -1,5 +1,5 @@
 use bevy::{prelude::*, render::view::RenderLayers, input::mouse::AccumulatedMouseMotion, pbr::NotShadowCaster};
-use crate::physics_plugin::{AccumulatedInput, Velocity, PhysicalTranslation, PreviousPhysicalTranslation};
+use crate::{physics_plugin::{AccumulatedInput, PhysicalTranslation, PreviousPhysicalTranslation, Velocity}, GameState};
 
 #[derive(Debug, Component)]
 pub struct Player;
@@ -20,9 +20,9 @@ struct WorldModelCamera;
 pub struct PlayerPlugin;
 impl Plugin for PlayerPlugin {
     fn build(&self, app: &mut App) {
-        app.add_systems(Startup, init_player)
-            .add_systems(Update, move_camera)
-            .add_systems(RunFixedMainLoop, handle_input.in_set(RunFixedMainLoopSystem::BeforeFixedMainLoop));
+        app.add_systems(OnEnter(GameState::Playing), init_player)
+            .add_systems(Update, move_camera.run_if(in_state(GameState::Playing)))
+            .add_systems(RunFixedMainLoop, handle_input.in_set(RunFixedMainLoopSystem::BeforeFixedMainLoop).run_if(in_state(GameState::Playing)));
     }
 }
 
@@ -65,7 +65,7 @@ pub fn init_player(
                     ..default()
                 }),
             ));
-            
+
             // we use a second layer ("framebuffer") to draw the player's arm on
             // there also a second camera that only views this buffer
             // this makes it easy because the second camera doesn't move with the player
@@ -126,8 +126,8 @@ pub fn handle_input(
         let right = transform.right(); // Right direction (x axis)
 
         if keyboard_input.pressed(KeyCode::KeyW) {
-            input.x += forward.x; 
-            input.z += forward.z; 
+            input.x += forward.x;
+            input.z += forward.z;
         }
         if keyboard_input.pressed(KeyCode::KeyS) {
             input.x -= forward.x;
@@ -146,5 +146,3 @@ pub fn handle_input(
         velocity.0 = input.normalize_or_zero() * SPEED;
     }
 }
-
-