I don't know if that was asked before or mentioned before, but i want to ask if you want to add a "suicide" button.
There were some levels where you actually had the opportunity to go somewhere, where you were not supposed to be going. (I know that there is an arrow above each checkpoint, which is pointing in the direction you should go, but sometimes I just checked every area, where you could possibly hide a chest.)
In one level I could fly all the way to the right border and fell to basically the bottom of the map and were stuck there, because I could not fly back up. So I had to close the game and start the map again. In such situations it would be helpful to have a suicide button to get back to the last checkpoint, so you don't have to close the game and start the level all over again, because you flew somewhere you weren't supposed to.