add game scene

scripts/GameManager.gd

@@ -1,4 +1,21 @@
 extends Node
 
-func _ready():
-	pass
+const GAME_SCENE_PATH := "res://scenes/Game.tscn"
+const MAIN_SCENE_PATH := "res://scenes/Main.tscn"
+
+func start_new_game() -> void:
+	var packed_scene := load(GAME_SCENE_PATH)
+	if not packed_scene or not packed_scene is PackedScene:
+		push_error("Failed to load Game scene at: %s" % GAME_SCENE_PATH)
+		return
+	get_tree().change_scene_to_packed(packed_scene)
+
+func save_game() -> void:
+	print("Game saved (mock)")
+
+func exit_to_main_menu() -> void:
+	var packed_scene := load(MAIN_SCENE_PATH)
+	if not packed_scene or not packed_scene is PackedScene:
+		push_error("Failed to load Main scene at: %s" % MAIN_SCENE_PATH)
+		return
+	get_tree().change_scene_to_packed(packed_scene)