Great concept and interesting level designs. There are only buttons, gates and slimes, but you managed to make good use of those to design the levels. Stripping jump away from the player is always a risky move, but that's what made this game interesting.
Something I find irritating is that when I am in a pit with only red slime, I'm essentially stuck there and have to reset all my progress on the level. The sprites for the gate also kind of blends in to the background.
All in all, it's a great game. Good job making it!