Great job, it's a really great game!
It gets really hard very quick, if you keep working on it I'd maybe ease into it a bit more. I gave up on the secret room you can access from the 2nd room. Largely because it was so hard, but also partly because I didn't see how you'd get out again after getting to the respawner. I assume the crystal would have warped me out?
Also I'd change or add another second change world key. If you use W,A & D it's a bit awkward. Maybe Ctrl would be good since there's 2.