Fixed bugs, softlocks, and changed game.

During some playtests after Wheelie was finished, I encountered some game issues.

Technical issues:
- Pressing "Next Level" after finishing 2 levels would restart the second one you were
   on, so a change was made where the Next Level button was swapped to "Levels", where you would be able to select a new level to play.
Softlock issues:
- Multiple softlocks were discovered, which were quickly fixed and now you are able to roll around as you were without getting stuck.
Gameplay changes:
- As I said, the Next Level button has been swapped out for "Levels", where you can select a level to play in the level menu accessed by
   pressing the button.
- The 4 level buttons now have titles displaying whether you have played them or not for progress tracking so you hopefully don't end up
   accidentally playing the same level twice.

Let me know if you have any suggestions for the game! Thanks for playing, goodbye!