Hmm..
I've been sort of watching you make this series for a long time, and I've seen how much it's grown. You almost have a party system going there, with the three characters all leveling up, all being different classes, races and with different weapons. The normal attack system is unique and will keep most players from fighting mindlessly while multitasking, such as if the attack button was the space bar. I enjoyed the fact even though you had your Lethal character pretty much set out, you still had those other two you could alter to your liking, making them sort of his minions or helpers.
The next step in my opinion, would be perhaps a party system, of all three characters fighting together instead of tag-teaming. This if course means stepping up the monster challenge a bit with either more than one at a time or just more per battle. I know that's easier said than done, but I'm sure as you advance, that option will look pretty likely. Hope the series works well for you and I'll continue to watch you from afar and see your progress.
