A good game, but too many bats.
This kind of game would benefit by adding some way to defeat the bats. I like that they move randomly, but you might also want to add enemies that just sit or only move in one direction. You might want to have fixed spawning points, so that the player can learn how to act and not rely off blind luck. Try playing a game and taking notes and just focus on one simple thing at a time, like how each enemy moves in a stage, or where that enemy typically is spawned at.