I made it to 12 :)
Nice job!
I like the concept although I feel like the nature of the games makes you unlikely to want to stand still very long anyways, otherwise the enemies would catch up to you. So I didn't really find that mechanic came into play much to be honest! I was thinking if I stopped moving for even a second I'd lose health but it's actually quite a bit of time it seems. I also did not see where to buy upgrades maybe I missed that.