http://en.wikipedia.org/wiki/Fitts’s_law
http://www.slideshare.net/lrizoli/fitts-law-basics
http://en.wikipedia.org/wiki/Pie_menu
http://msdn.microsoft.com/en-us/library/ms993291.aspx
http://en.wikipedia.org/wiki/Point_and_click
http://en.wikipedia.org/wiki/Human-computer_interaction
