Cool game! I know you're trying to keep it simple but a couple suggestions that might help and won't increase game complexity too much:

  1. Add a share button to share your score
  2. Add a timer component (can be hidden).  It will add urgency.
  3. Speed up the ball as time goes on (maybe i haven't gotten far enough for this to happen...?)
  4. If you're adding more points for "same rotation hit", make it clear that it's doing that and don't just add more points to the score (shake the number, throw some fireworks, or something).  Your focus is on the ball not the score so you won't even notice the number went up a little bit more than usual until you lose.