Hefty update for Marcus O'Snail

Marcus O'Snail has gotten it's final major update for now. I have added a grade system to the levels based on how quickly you finish them. Can you get 3 shells (not stars of course) on all levels?

The other major part of this update is that I have removed two levels that didn't actually didn't actually have puzzles in them (bad for a puzzle game I guess). They are replaced with more challanging levels!