This is super-solid. I'd say you would have a hard time making it a commercial game without improving the game loop a bit, since the current iteration would be repetitive over time and the balance is off as you progress. My biggest gripe is the first boss can take forever to beat. Healing is so easy to do you should have just made health restore at the end of each battle. Overall it's incredibly well polished. I obviously enjoyed myself because I played it right to the end. I loved the end bosses 2nd state and all the work that went into it.