This app reminds me a lot of that old computer game, Ballance, but a mobile version. But I do have big suggestions, so I will list them out.
1. Music and sound effects
This would make the game more exciting. For example, a death sound when you die, or a rolling sound on the metal rails and wood.
2. Different ball types
Like in Ballance, there should be different ball types. Here, we should have any type of ball, like more than 3!
3. Checkpoints
These checkpoints can be very important to this game. They can look like anything! Like, similar to the spawn point.
4. Shadows
In the preview, I saw shadows. I think you should add some to this game!
5. More levels!
Right now, the 34 levels are good, but why not add a bit to get 70? All levels added would be new, and would have new things!