Add split-screen Space Shooter with pod steering and boost.

Two-player mode with client assignment, 3D vector calibration for cylindrical
pods, lives, tap/double-tap boost with low-intensity LED cooldown feedback,
and Kenney sprite assets.

Co-authored-by: Cursor <cursoragent@cursor.com>

scripts/menu.gd

@@ -4,11 +4,13 @@ const DEMO_SCENE := "res://scenes/demo.tscn"
 const CONFIG_SCENE := "res://scenes/config.tscn"
 const PONG_SCENE := "res://scenes/pong.tscn"
 const COLOR_GAME_SCENE := "res://scenes/color_game.tscn"
+const SPACE_SHOOTER_SCENE := "res://scenes/space_shooter.tscn"
 
 @onready var demo_button: Button = $CenterBox/DemoButton
 @onready var config_button: Button = $CenterBox/ConfigButton
 @onready var pong_button: Button = $CenterBox/PongButton
 @onready var color_game_button: Button = $CenterBox/ColorGameButton
+@onready var space_shooter_button: Button = $CenterBox/SpaceShooterButton
 @onready var exit_button: Button = $CenterBox/ExitButton
 
 
@@ -17,6 +19,7 @@ func _ready() -> void:
 	config_button.pressed.connect(func(): _open_scene(CONFIG_SCENE))
 	pong_button.pressed.connect(func(): _open_scene(PONG_SCENE))
 	color_game_button.pressed.connect(func(): _open_scene(COLOR_GAME_SCENE))
+	space_shooter_button.pressed.connect(func(): _open_scene(SPACE_SHOOTER_SCENE))
 	exit_button.pressed.connect(_exit_game)