Interesting concept. I like that the charge is used up in more than one way (shooting, walking) because it made me really think about when I needed to be moving or when I really thought I'd be able to land some shots. That said, I don't know that the boss fight really seemed designed with these mechanics in mind; there didn't seem to be good times to stop and charge, and some of the charging in general could probably use some balance. But I really do love the concept. I could see it going somewhere if you have plans to work on this more!