Nice Game
I love the whole blind concept. I really felt i was walking blindly through this game.
One thing to note: Occasionally I ran into a bug which prevented me from shooting the ball at all, not sure what caused it but this left me somewhat even more dependent on the sonar mechanism.
Improvements: Perhaps the ability to see the levels without being blind once you beat the game? Would be fun to see all the levels and where I've been stumbling around 21 levels would look like!