Hi nice game. Overall I'd say the level design is good I like that you don't try to introduce all they types of objects to the player at once. Also, I think the art works for this game; I had no trouble figuring out that the red spidery things are mines/bombs, and generally determining what's what. So you need to re-evaluate your artistic skills
A couple of bugs/fiddly things
There doesn't seem to be a red door-key inventory. that is to say if I pick up 1 key I can open 1 door, if I pick up 3 keys I can open 1 door. This is problematic on the level with 3 doors that need red keys.
I have trouble entering narrow corridors like the one in level two leading from the start location to where the red key is. The character get's off by 1 block and the typical character step is 2-3 blocks; so after moving up/down I'm now off by 1-2 blocks in the opposite direction. I have the same issue with the door on level 2, and probably other places.
I second meva's comment about not wanting to play every level from the beginning again. I'd settle for something that lets me try the last level I was on over again, and resets when the game closes.