Great concept! I also love the art and the subtle detail of the music slowly speeding up
Since the game itself is quite repetitive, it would definitely help to bump up the player speed to stop it from feeling slow (You may need to make the map bigger or make the timer shorter etc to counteract this). I would also always recommend allowing for both WASD and the arrow keys to be used since a lot of players are already used to WASD.
Overall though, super cool game!