I think the core idea here is solid but for showcasing another dimension, perhaps a different color would be better than light or dark. An easy solution if you want to stick with brightness/darkness is to let the player control the brightness of their game so each person can tweak it to better fit their own eyes. I would agree with the previous poster too that a key for abilities rather than mouse clicking would really improve the playability. Having to keep track of the mouse cursor on top of the player's locations/surroundings all while holding the button down just adds frustration for me rather than a satisfying challenge. Otherwise, love the look of the game and the speed puzzle idea seems like a a fun direction to go.