Really cool concept. I like that melody change when you flip. Minimalist Art is a little bit too minimalist for me but make the level readable. I think that your lever could always do the door appear. And use Camera exclusively for moving walls . I notice there is some blocks where you can't flip (a darker one, sometimes on the screen boottom, with the boss), it's cool to have such blocks, but i would be better to recognize them at first sight (with a distinguishable color or texture). Hope it helps :) . I like your game. Great job.