I love this concept! Somethings I might suggest is on the key bind changing option menu, I would give some indication of what exactly each key is for. The up/down/left/right is straightforward but the other two controls on the x and z keys don't really say what exactly they do. Players would probably want to know what control/action they are changing the key bind for. Also some indication of how many keys the player has collected would be nice since it's sometimes hard to remember how many were collected. And when you die to the water in the beginning, your hearts don't decrease and you keep the key. Otherwise great game!