- Add InventoryBackpack under HUD CanvasLayer (layer 5) in Game.tscn - Add InventoryOverlay under InventoryOverlayLayer CanvasLayer (layer 10) - Fix Tween.TRANS_SINE_IN -> .set_trans(TRANS_SINE).set_ease(EASE_IN) in InventoryBackpack.gd (Godot 4.6 split transition and easing APIs)