EASING:
| "linear"
| "inQuad"
| "outQuad"
| "inOutQuad"
| "inCubic"
| "outCubic"
| "inOutCubic"
| "inQuart"
| "outQuart"
| "inOutQuart"
| "inQuint"
| "outQuint"
| "inOutQuint"
| "inSine"
| "outSine"
| "inOutSine"
| "inExpo"
| "outExpo"
| "inOutExpo"
| "inCirc"
| "outCirc"
| "inOutCirc"
String identifiers for easing functions