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>

scenes/menu.tscn

@@ -29,9 +29,9 @@ anchor_top = 0.5
 anchor_right = 0.5
 anchor_bottom = 0.5
 offset_left = -180.0
-offset_top = -240.0
+offset_top = -280.0
 offset_right = 180.0
-offset_bottom = 240.0
+offset_bottom = 280.0
 grow_horizontal = 2
 grow_vertical = 2
 theme_override_constants/separation = 16
@@ -83,6 +83,13 @@ size_flags_horizontal = 4
 theme_override_font_sizes/font_size = 18
 text = "Color Game"
 
+[node name="SpaceShooterButton" type="Button" parent="CenterBox"]
+custom_minimum_size = Vector2(280, 48)
+layout_mode = 2
+size_flags_horizontal = 4
+theme_override_font_sizes/font_size = 18
+text = "Space Shooter"
+
 [node name="ExitButton" type="Button" parent="CenterBox"]
 custom_minimum_size = Vector2(280, 48)
 layout_mode = 2