If you click on the ball immediately after it hits the ground, you can reset the ball back to the top. This essentially doubles your profit of a ball since you don't have to wait for it to bounce back upwards.
When you get the impossible badge there is really small text that says "You have unlocked something but I'm not going to tell you what it is." what you unlock is a way to skate on runner levels and a way to run on skater levels. Go to the pause menu and click on the "?" to change.
The only problem is that on basic mode, when you miss a long note you tend to hold the key down (or at least I do) and your meter goes down really fast. Great game other than that 5/5
(Clicking the ? also activates midair jumps.)