Good level progression and puzzle design! A problem that kept happening to me - and even costed me a game - was that, sometimes, i was locked from moving into some avaiable directions and had to press W-A-S-D randomly until the game accepted a valid input. Usually, I'd just move in a invalid direction, such as a border, and the game would go back to normal, but, in the puzzle with the invisible things, the game forced me to move into a direction I knew had a trap.