There are 52 achievements waiting to be unlocked.
Unlocked achievements are shown with the card faceup.
The cards unlocked since your last visit are shown with a "dancing" animation.
Some achievements can be partially solved and are shown in a darker color.
As you progress the card becomes brighter.
To see the exact percentage been solved, click the card.
The card will zoom and display all important information about the achievement.
Eight achievement are secret (shown with a question mark), you can't see what needs to be done to unlock them.
Each of them is revealed by unlocking some other achievement.
Each achievement has a value which is used to calculate the achievement score (the sum of all unlocked achievements).
This score is used in the Achievement leaderboard.