If I were inclined to make lazy cross comparisons (and I am) I would say that Boss Battle is like a top down shooter, stripped back, combined with Shadow of the Colossus. It's a game that makes the boss battle central to the game. In fact - there is nothing else but a boss battle. That's why the game is called Boss Battle.
I wasn't too enamoured with this one to begin with. In fact, after two minutes I was about ready to start looking for something better - but then it clicked. Boss Battle looks terrible - but the enemy and wave programming becomes increasingly inventive as you play. It's like an exercise in stretching an idea to breaking point.
I'm really enjoying it.
Boss Battle [Boss Battle]