Great idea that requires a lot of balancing!
I believe the play area to be too small for such a "fast-paced" game. A lot of times you don't have time to react - and you need that!
But you've got excellent vision of scope - this is indeed a jam game, and all it needed to be was simple and fun. You've got that!
I also recommend much more game feel, it's another thing your game sorely needs (besides more mechanics / obstacles and stuff, but then again, jam). Overall, nicely done!