Here is a list of all rotations systems known to be in use by various Tetris implementations: <a href="http:&#x2F;&#x2F;harddrop.com&#x2F;wiki&#x2F;Category:Rotation_Systems" rel="nofollow">http:&#x2F;&#x2F;harddrop.com&#x2F;wiki&#x2F;Category:Rotation_Systems</a>