Interesting concept! Other than the feedback you have gotten on how to add more depth to the game, I would make the fist target sprite a little bigger and more telegraphed. It was sometimes hard to tell where it would land and the time you get to react felt too short.
Some bugs that I found:
* The hazard would sometimes get stuck on the floor and never leave and no other hazards would spawn again.
* I managed to eat a bug right about the same time my "health" ran out. I regained health but the game still ended.
Other than that, I really enjoyed the atmosphere you created with your graphics and sound effects. Nice job!