Click on one of the links to play a challenge.
You earn stars by completing challenges with a good enough score.
Some challenges (e.g. B1) are unlocked by earning enough stars.
(Your star count is shown at the top right.)
Some challenges (e.g. A2) are unlocked by getting a star on the prerequisite (A1).
If it's your first time here, try the tutorial
5 stars: ???
25 stars: ???
125 stars: ???