This is an interesting game with some really neat ideas. It's a turn-based game, but it's also kind of a puzzle game. There are 8 bosses to fight. You can pick which one and you unlock abilities by beating some of them. It's not fully like Mega Man where you beat a boss to easily beat another boss. There's also an interesting story to learn. All that is just chapter 1!
Chapter 2 finds ways to remix bosses and takes place a year later. The story is more linear, but even more fleshed out and interesting. The final, final, final boss is really challenging, but the ending is worth it once you figure it out.