Well....
Thier was a glitch come level 21 that made you invincible threwout the rest of the game. Further-more it did get a bit boring at times. And anouther thing. The game was hard! Like very! The level of complexity gained in rank far to fast. Then the sudden change in style created a much more complex setting as-well. And lets face it, in time the music got repeditive, and the animation had no cool effects or effort to it.