Unity Web Player | The Bleeps menuing design test

The is a quick mockup to demonstrate and test out the level menuing system for The Bleeps, an mobile game in development with Battery Powered Games. The other menu screens were also added to give a complete esxperience of the UI flow.

This level selection concept is different than what I would consider the standard model, where the levels are sequentially earned. The concept for The Bleeps connects levels in a more dynamic and selective way. But, this also comes with a potential problem, since a Next Level button doesn't really make sense any more. How does it feel for a player to go back to the level select screen?