Just a small update fixing a few things.
Thanks to Na for finding that 6-2 and 0-8 were impossible and proposing a solution.

- Reworked 6-1 to make it more interesting.
- Added a move to the box in 6-2 to make it possible
- Added a power box to 0-8 to make it possible
- Added Na to the credits under Extra Thanks
- World 0 level tint now displays as it was not showing before
- ? levels and World 8 now have the correct wall tint color
- 1-? now displays the correct UI element