Easing関数群。 参考: http://gizma.com/easing/

Functions

easeInCirc
easeInCubic
easeInExpo
easeInOutBack
easeInOutCirc
easeInOutCubic
easeInOutExpo
easeInOutQuad
easeInOutQubic
easeInOutQuint
easeInOutSine
easeInQuad
easeInQuart
easeInQubic
easeInQuint
easeInSine
easeOutBounce
easeOutCirc
easeOutCubic
easeOutQuad
easeOutQuart
easeOutQubic
easeOutQuint
easeOutSine
linear