Thisone took me by surprise. I epected this to be a game whereyou can only press each of the arrow keys once (many of these gmes have been made in this jam), but this takes the idea to a much more interesting place. You can "unpress" each key only once. It forces you to consider movement and the overlapping of key ussage really really hard.
The idea is even exapnded upon in later levels where you can unpress more than once. Very clever and very unique.