Nice game, I loved the concept. I realized later that when human dies it spawns a soul which we can collect and use it to create another ghost.
I have some ideas if you want to develop the game further.
1. Some indicator would be nice to see how many souls we have left
2. At start only one or two souls would make the game more interesting, however capacity can be increased via upgraes
3. Different variety of enemies
Overall great game :)