Nice and simple. Buttons to kill enemies is a cool mechanic and was introduce very well (same with the teleporters) but sometimes the backtracking can be repetitive and tedious. I think using this mechanic will multiple enemies simultaneously would also be an interesting idea; make the player combine the skills you taught them. I wish the doors were a more obvious end-goal, it could use some extra particles or highlighting. Audio was quite repetitive towards the end of the game.