It's a really fun game, and I love the art style too. The only issue is that sometimes when you unlock a mechanism somewhere, there's no hint about it. You could play a short animation when a mechanism is unlocked, with the camera tracking back to the player. I got stuck on the second level after collecting the three keys — after handing the keys over to a door, I had no idea what to do next, and then somehow the game just restarted, making me redo the entire second level! I think it would help to add some checkpoints.