I adore your art style: visually simple and clean but very effective — and cute!
I think the game is a bit slow, as it starts very easy and takes a while to get to a point where you have trouble keeping the ghosts away.
I would probably made the area of light a shade of dark gray, slightly lighter that the black background, to show how it is shrinking. It is already visible when ghosts start to get “clipped”, but at first i did not realize why.