It's not perfect...
Extremely addictive and fun to play and the inclusion of the ultra easy mode is a nice touch, but there are several issues that need be addressed.
The control system is good, and the idea of clicking and dragging the mouse for dashes, uppercuts and slams was good, but the problem comes with dashing. Since the game requires you to click the mouse to attack it is far to easy to accidentally to click down and move the mouse just enough to cause a dash and send you flying around the screen, which I find quite annoying.
A refinement for the controls would be an arrow key + asd button system, were arrow presses and certain other key presses would unlock combos.
The lack of a proper health bar. Painting the screen redder and redder, though a good idea, obscures a persons vision of the game, making it more likely you will die.
The upgrade system is nice idea, but with no actual stats available on the character how much addition to health and attack do those upgrades mean. also the costs of certain things are prohibitively high.
Its a great game, it just needs a little more work and polish.