I really like what you did with the theme. The game is fun, engaging and challenging.
Jumping it's a bit hard, as you always jump the max distance. It should be proportional with the time you're actually pressing the jump button. Also, some colliders are interrupting the jump and it's hard to predict whether or not you'll succeed. By the way, I got no damage from falling from high ground. I reached the top of the world and then fall, but didn't die.
The level layout is great and enemies are well placed.
You should add more feedback for actions. For example, when you improve your stats, there's no way to tell if you reach the max level (I guess I did because I couldn't buy any more in some stats). In addition, add some sparks or other FX when enemies are hit, that way the player will know it.
Maybe you should add an extra option for "checkpoint". Like, spending 200 energy on creating a clone. That way, if you die, you don't have to restart from zero which is a bit frustrating.
And, of course, the art is amazing. I read your article about it too.
Great job!