Enjoyed it for a bit. It think the shooting is good and the ghost mechanic can be really good but it needs slightly better implementation.
I played it on a phone so I'm not sure if it's universal but there's not a lot of movement feedback. The waves feel a bit too short. Any sort of Sound track(ideally an 8/16 bit one) would help.
Have some sort of pixel art for other elements of the game as well.
The game can be enjoyable but can be better with more polishing and new mechanics.