Mosaic Pieces are unlocked by gaining Levels during an Event.
During a monthly Event:
- Complete (or replay) puzzles in the main game packs to earn Event Stars.
- Once you collect enough Event Stars you'll gain a Level.
- Sometimes when you level up, you'll unlock more puzzles in the current Event Pack.
If you have purchased the Event Pass (by selecting "Unlock Premium") this month, you will earn the Premium rewards on the track (Gold) as well as the Standard rewards (Purple). If you reach the maximum level before the end of the event, you'll have unlocked 100% of the mosaic.
If you complete the mosaic before the event ends, it'll be saved to the Gallery so you can view the finished mosaic later.