In addition to the non-unique solutions and style machine (should really count the number of unlocked styles instead of attempts), I have two other major issues:
- You can click the puzzle behind even when the message at the start and the finish is in display. For this reason you can sometimes finish the puzzle multiple times (giving additional points each time) if you've marked all colored times but not all crosses.
- The line mode doesn't exactly mark all tiles expected to be marked, as it can leave some gaps. It is also very easy to draw in the unintended direction (ruining your progress); you probably need some delay to check for the actual direction the cursor is going.