Not too shabby!
Not bad! A few things to fix/add:
controlls are a little buggy. Character should only move while key is pressed. Every time it starts, knuckles goes left, and keeps trying to run even if he's hit a wall and i'm not touching anything.
At times, i'd run one way while the character faced the other way - essentially running backwards.
Collision is a bit off -- sometimes i couldn't get around a corner even if I was in the right place. Other times, i'd touch an enemy, and not die if i moved away just right.
Needs some kind of animation for death and game over. That goes for sounds, too - as well as sounds for rings being picked up, power-ups, enemies "eaten", etc.
Excellent staring point!
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