Looks nice game, and there are something very simple but clever with Placing blocks - feature. Controls are such bad, because you have to change your hands position all the time and jumping is based on the space bar, which is good only if you use thumb on Space.
Why not to place items by pressing a keyboard button, while then there are not be the same capabilities as using the mouse, but would it matter sooner or later?
I'd like to see some more checkpoints here, because hazards are too close to transforming room edges and while there you really can't run in a room when you just very often had to. It would also be nice to see the flies to fly around, as they are flies. Placing the blocks are not placing correctly into grid either.