Nice prototype.
Looks like it can be pretty fun if you add some goal.
In the future. maybe you can find some other way to get the enemies in the combat, because the way it is now, you can stay still and clear the enemies before moving to the next square. This makes it more easy and therefore the idea is inviting, but also makes the game boring.
Also, its probably because of the multiple collisions checkings, but when there are multiple enemies and balls, the game slow down a lot.
All in all, this looks neat :)