Fun concept, but I found it impossible and random. As far as I can tell, it's random whether the enemies move first or shoot first, and whether they shoot at where you move from or where you move to. I kept taking hits that I couldn't avoid, spending all my money on healing, and eventually dying. Maybe I'm missing something, and maybe I would have done better if I'd gotten the shield or speed upgrades instead of healing. Still, I think the game would be better if it were more consistent and predictable.