Add build directory to .gitignore, create export presets for Web and Windows Desktop, adjust z-index and mouse filter in level_1.tscn, add update_game_state function in level.gd, change main_scene path in project.godot, set rendering method to "gl_compatibility", add LevelSelect and related nodes in main_menu.tscn, create scene_manager.tscn with MainMenu node, implement functionality for menu button selection in main_menu.gd.

scenes/scripts/main_menu.gd

@@ -0,0 +1,38 @@
+extends Level
+class_name MainMenu
+
+@onready var level_select = get_node("%MenuButton")
+@onready var high_scores = get_node("%HighScores")
+@onready var exit_button = get_node("%ExitGame")
+
+func _ready():
+	level_select.get_popup().id_pressed.connect(_on_item_menu_pressed)
+	high_scores.connect("pressed", Callable(self, "on_high_scores_pressed"))
+	exit_button.connect("pressed", Callable(self, "on_exit_pressed"))
+	update_game_state()
+
+
+func _on_item_menu_pressed(id):
+	## Load the appropriate level based on the selection that has been made 
+	Log.pr(id)
+
+	match id:
+		1:
+			# Load level 1
+			SceneMgr.load_scene("LEVEL1")
+			#get_tree().change_scene_to_file("res://levels/level_1.tscn")
+		2:
+			# Load level 2
+			SceneMgr.load_scene("LEVEL2")
+		3:
+			# Load level 3
+			SceneMgr.load_scene("LEVEL3")
+
+func on_high_scores_pressed():
+	## Load the high scores screen
+	Log.pr("High scores button pressed")
+	pass
+
+func on_exit_pressed():
+	# Quit the game 
+	get_tree().quit()

scenes/scripts/scene_manager.gd

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+extends Node2D
+class_name SceneManager
+
+const SCENES : Dictionary = {
+	"MAINMENU" : "res://scenes/main_menu.tscn",
+	"HIGHSCORES" : "res://scenes/highscores.tscn",
+	"LEVEL1" : "res://levels/level_1.tscn",
+	"LEVEL2" : "res://levels/level_2.tscn",
+	"LEVEL3" : "res://levels/level_3.tscn",
+	"LEVEL4" : "res://levels/level_4.tscn",
+	"LEVEL5" : "res://levels/level_5.tscn",
+	"LEVEL6" : "res://levels/level_6.tscn",
+}
+
+var loading_scene_res : Resource = null
+
+func _ready():
+	Log.pr("SceneManager is ready.")
+	SceneMgr.connect("change_scene", Callable(self, "_on_change_scene"))
+	$TransitionScene.connect("transitioned", Callable(self, "_on_transition_scene_transitioned"))
+
+func _on_change_scene(scene_name):
+	Log.pr("Going to load a scene.", scene_name)
+	if SCENES.has(scene_name):
+		loading_scene_res = load(SCENES[scene_name])
+		Log.pr("Loading scene: ", loading_scene_res)
+		$TransitionScene.transition()
+	else:
+		loading_scene_res = null
+
+func _on_transition_scene_transitioned():
+	$CurrentScene.get_child(0).queue_free()
+	$CurrentScene.add_child(loading_scene_res.instantiate())

scenes/scripts/transition_scene.gd

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+extends CanvasLayer
+
+signal transitioned
+
+func _ready():
+	$AnimationPlayer.play("fade_to_normal")
+
+func transition():
+	$AnimationPlayer.play("fade_to_black")
+	Log.pr("Fading to black")
+
+func _on_animation_player_animation_finished(anim_name:StringName):
+	if anim_name == "fade_to_black":
+		Log.pr("Sending transitioned signal...")
+		emit_signal("transitioned")
+		$AnimationPlayer.play("fade_to_normal")
+	if anim_name == "fade_to_normal":
+		Log.pr("Faded to normal")
+