feat: implement main scene initialization and add screen shake and stop-n-go game managers

scenes/main.gd

@@ -171,6 +171,11 @@ func _hide_ground_tiles():
 func _setup_effect_elevation():
 	var em = get_node_or_null("EnhancedGridMap")
 	if em and em.mesh_library:
+		# USER REQUEST: Do not apply visual Y-elevation for walls in Stop n Go mode
+		if LobbyManager.game_mode == "Stop n Go":
+			print("[Main] Stop n Go mode detected: Skipping effect elevation for walls.")
+			return
+
 		var ml = em.mesh_library.duplicate()
 		
 		# Height 0.8: Above 3D arena, but below pickups (Y=1.0)
@@ -183,6 +188,7 @@ func _setup_effect_elevation():
 		em.mesh_library = ml
 		print("[Main] MeshLibrary elevation applied: Wall(4) and Freeze(5) at Y=0.8")
 
+
 @rpc("any_peer", "call_local", "reliable")
 func sync_portal_configs(configs: Array):
 	if portal_mode_manager:

scripts/managers/screen_shake.gd

@@ -30,4 +30,3 @@ func set_target_position(new_pos: Vector3, duration: float = 1.0):
 	# Tween the target position
 	var tween = create_tween()
 	tween.tween_property(self, "target_position", new_pos, duration).set_trans(Tween.TRANS_SINE).set_ease(Tween.EASE_IN_OUT)
-

scripts/managers/stop_n_go_manager.gd

@@ -360,8 +360,8 @@ func _apply_arena_setup():
 		for z in range(gridmap.rows):
 			var current_pos = Vector2i(x, z)
 			if current_pos in non_walkable_coords:
-				gridmap.set_cell_item(Vector3i(x, 0, z), -1) # empty space / void
-				gridmap.set_cell_item(Vector3i(x, 1, z), TILE_OBSTACLE) # wall block
+				gridmap.set_cell_item(Vector3i(x, 0, z), TILE_OBSTACLE) # wall block on Floor 0
+				gridmap.set_cell_item(Vector3i(x, 1, z), -1)
 				continue
 
 			var tile_id = TILE_WALKABLE
@@ -379,7 +379,7 @@ func _apply_arena_setup():
 	_create_room_with_edge_walls(gridmap, 7, 6, 11, 9, r1_entrances)
 	
 	# Non-walkable obstacle inside Room 1
-	gridmap.set_cell_item(Vector3i(9, 1, 8), TILE_OBSTACLE)
+	gridmap.set_cell_item(Vector3i(9, 0, 8), TILE_OBSTACLE)
 
 	# Room 2: (15,1) to (19,5) - 5x5 Area. Boundaries: X[15..19], Z[1..5]
 	var r2_entrances = [Vector2i(15, 2), Vector2i(17, 1), Vector2i(19, 2), Vector2i(18, 5)]