Here are some Tips:
-Make the player able to jump, even after he left the ground, else it feels unresponsive.
-maybe make the Jumpheight variable.
-When the Player pressed th jump button in the last x sec. make him jump when he touches the ground
- I loved the forward and backward mechanics with the ball, they fell so great
-the idea is great, i love it
-maybe make it so that the level is a bit harder when you have to play it backward in order to kill yourself