http://en.wikipedia.org/wiki/Category:Word_games
http://en.wikipedia.org/wiki/Constrained_writing
http://en.wikipedia.org/wiki/Category:Mathematical_games
http://en.wikipedia.org/wiki/Category:Surrealist_games
http://en.wikipedia.org/wiki/Category:Surrealist_techniques
http://en.wikipedia.org/wiki/Category:Artistic_techniques
http://en.wikipedia.org/wiki/Optical_illusion
http://en.wikipedia.org/wiki/Category:Optical_illusions