(This is my first game so don't exspect much out of it) don't touch the snails and try to colect all 17 coins.
Try to change so you can access all the platforms. On the actual state, there's no way. Maybe changing the position of some of them and giving the behavior Jump Through. Also, on one of the platforms, there's a little bump that (when you touch it) you can't keep walking forward: you have to jump. The button "Next" is a new level or a continuation of the first?