Nice UI, aesthetics & sound. The concept is good but although I got 2nd in the leaderboard, I felt that I was more due to luck than skills: the player has too much inertia to properly dodge so many obstacles, and once you get hit once you can barely see the ninja because half of it is out of the screen.
Ideas for improvement: ability to move lateraly in addition to vertically, hitting an obstacle makes you lose health instead of slowing, and tighter controls (more drag & magnet force). Then you can add bonus to increase health or increase the magnet force, and you get a full game :)