Thanks for playing!
Yes, the healthbar is the amount of light you have in your torch. It refills after every 4 levels. Fair play for making it so far in the dark!
The tileset is a bit misleading, you're not meant to stand on the side of the spikes in that level. The way it's supposed to be solved is by jumping down through the spike column and quickly jumping again to avoid the arrow. That's on me though, it does look misleading, and it's something I would have polished up with more time.
Thanks for all the feedback, it's very useful to me!