I cannot believe how much time I spent playing this. In fact, I am still playing this! You have done such an amazing job with such a simple idea.
If I can, my only feedback is that the battle system is REALLY hard for me. If there were keyboard shortcuts to block I wouldn't complain, but having to mouse to block is too much. I ended optimizing by letting one on the left or right die and then praying I could block enough to kill the boss.