The pieces all look terribly similar but some appear only once. Remove these single pieces and leave all pieces that are doubled. In this relaxing game time is not an issue, only your skill to detect different patterns.
Click to remove single pieces from the board. Level is finished once only pairs are left. In each new level you get more points for removing pieces. If you incorrectly pick a paired piece, depending on your luck game may end or your score may be halved or hopefully nothing happens.