Very nice! It feels nice and complete with a great explanation and tutorial. A+
I love the mechanic of getting stronger when you have less health, it means you have a way out of getting backed into a corner. I didn't get too far into the game, but I can easily see inclusion of some boss fights, more jumping obstacles etc.
Also, I found it best to stay on the ground and not jump at all. So if you want the player to have to jump or at least make use of it, perhaps make some obstacles that you have to get over to get on the other side of, with some reason to expose themselves by jumping.
Great Game!
if you have time, could you please check out my game?