I quite enjoyed this. The concept is very good -- trying to avoid getting healed is interesting, and leads to some fun mechanics. It seemed to me as if the arrows healed me, which was a cool touch, but also not immediately obvious (I also didn't immediately notice the healing items, but that's just my bad; they're very obvious).
I particularly liked that levelling up healed you, which gives a nice effect that's usually in management games -- using your "money" to get more "money" making things. In this case, levelling up and healing so you can take more damage. Clever.
I would have liked to see some more variety in upgrades (it was limited by the time constraints, I imagine), but also some way to make standing still not a viable strategy. I guess the timer does that? But perhaps having the experience come from something else than picking up stuff? E.g. over time by itself? But it might be fine as is as well.