Interesting in places, but very flawed.
First of all, if you're going to do a physics-based game with this many moving parts, you need a low quality button.
Second, the main issue was the boss fights. Chaotic kinematics like the brothers' swinging arms or the snake's tail are generally a bad idea in games, as unforeseen parameters can cause those things to just be unplayably erratic. The final boss's first target wasn't even on screen for minutes at a time, and when it emerged it stayed inside its own coil for another two. This goes double if you're feeding them periodic movements dangerously close to their natural resonance -- by the time the brothers' cores were both vulnerable, their arms were often swinging unavoidably fast and never slowed down. If you don't know enough physics to be able to work out that kind of system and identify and avoid its dominant modes (it's usually 400-level classical mechanics in college), it's best to just avoid implementing one altogether.
Third, your ads and facebook/twitter buttons had a nasty way of popping over content (and the ads were very laggy). You might want to find a different sponsor if they're going to be that obnoxious.
Fourth, you seem to have a memory leak somewhere. Check your disposal on ending or resetting a level.
Five, the final boss's homing missiles were really obnoxious. I get that spinning them to a sufficient arc at close range will make them stop, but if they recover before you tap their core they'll just abruptly point at you instead of gradually aiming back. Instead of aiming them directly each frame, consider giving them a max angular velocity, pop it to zero when you spin them enough, then when they recover, blend it slowly back to the max over about a second or so.