This is very promising !
Gameplay is fun, although pretty hard, even easy mode can be tough if you're not careful. Health and ammo are barely enough to finish the level, but maybe that's intentional.
Environment is a bit bland right now with grey bricks everywhere, also the music is really anticlimactic.
For the record I had the door bug on version 0.55E too, but 0.55F fixed it.
Looking forward to see where this goes.