Earned all six difficulty stars on any 10 Classic Jigsaw puzzles.
To make this achievement easier, once you have earned 3400 Gold you can download the Kids Pack
collection of 10 puzzles, since the Expert puzzles only have 48 or 49 pieces. Thanks to Borg561
for this suggestion.
Complete each of the 10 puzzles on Easy
difficulty first, which will unlock the other puzzles. You now need to complete them again on Medium