Making the map cost you time while it's open is a really clean idea, and the darkness sells it. Only being able to see one room at a time is unsettling in a way a normal top down view never would be, and the turtle moves nicely. I have to be honest that I never got to test the map trade properly, and the reason is worth flagging. In the browser embed at default size the HUD is cropped, so I never saw a timer at all, and my first run ended on a Game Over screen that was itself cut off at the edges before I'd understood that time was even a factor. I know the page says to play in fullscreen, but the windowed version is what most people rating are going to open first, and right now it hides the thing the whole design rests on. Anchoring the clock further inside the frame would protect it.