Hmm..
Starts very simply. Fun. Not too difficult. Nice learning curve. You start to feel like a real space ninja (if that makes any sense at all). It's when you reach the cannons that fire rocks at you chaotically that things get tricky and frustrating. It's hard to tell when shrapnel is going to hurt me or not- whether it's the actual attack or just the nice animation at the end of an attack. Then there's a flight of stairs where every step has a cannon on it. And then the boss fight at the end makes use of them. It was agitating at best and nearly got me to quit at worst.
In the end I beat the game, and having only unlocked one medal, I felt a little like I'd wasted my time. It's a nice game, but it would have been cool to include some notes about the game's design or something as a reward.
As it is, this is a solid game. Good job. 8/10, 4/5.