EaseBackInOut method
Implementation
double EaseBackInOut(num t, num b, num c, num d)
{
num s = 1.70158;
if ((t/=d/2.0) < 1.0)
{
s *= 1.525;
return (c/2.0*(t*t*((s + 1.0)*t - s)) + b);
}
final postFix = t-=2.0;
s *= 1.525;
return (c/2.0*((postFix)*t*((s + 1.0)*t + s) + 2.0) + b);
}