A very nice concept with a lot of potential and fitting soundtrack as well. After getting used to it, I had fun playing it.
A tutorial level/video would've been nice as initially, you don't really know what to do. Also, I think having a life bar or hearts would've been better to maintain the flow of the game.
Also, since the ghosts can move through walls but you can't shoot through walls, it sometimes feels a bit frustrating to shoot, especially in the beginning. It would be nice if you find a way to reduce this somehow(maybe a particle effect on the wall?).
Overall, great work!