Nice game.

Here is a list of things you should add:

Sound and music.

Polish ie screen shake, Particles, etc.

Making the theme more important.

Making the game funner.

I like the idea a lot. I would speed up the game and make left-right controls more tight, I think it would be more action packed. But that is a personal preference of mine. However I enjoyed the game a lot controlling 2 characters was well executed, well done!