Obviously, the game lacks music and sound, but you probably already know that.
With that out of the way, I REALLY LIKE THIS GAME! The sword and shield combat, combined with the healing mechanic gives a really neat rythm to the combat; you go in, dish out damage, get damaged, step back and heal.
The cooling down is also really well done; when I first read about it in the description I got a bit worried. If it was too slow, then it'd break the pace of the game. If it was too fast then it'd be broken. Thankfully, your game fits neither: It works. It takes the perfect amount of time; it's not slow enough to break the pace of the game, but also not fast enough you can do it whenever you want to; you need to consider when it's safe to stop and cool down.
My only problem with the game (other than the lack of sound) is the third fight; as I don't have anything to damage the boss with, that means it's up to the boss to kill itself, and that's just not really engaging; with the other fights it felt like I was damaging the boss, it was my task to kill the boss. Here it's just waiting; withouth a hands-on objective (damaging the boss), a survival task like that really isn't engaging.
Other than the third fight, I really, really like this game. It has a great flow to it, and combined with the great art style, this is a great game.