To complete a level you must make all the tiles in the play area turn smiley.
You can change the face of a tile by clicking it,
but that will flip the 4 adjacent tiles too.
The fewer flips you make, the higher your score will be (score is tallied when you complete a level).
Completing a level unlocks it so you can play it again later.
Complete 20 levels to win the game.
Good Luck!