public static double BackEaseInOut(double t, double b, double c, double d) { var s = 1.70158; if ((t /= d / 2) < 1) { return c / 2 * (t * t * (((s *= (1.525)) + 1) * t - s)) + b; } return c / 2 * ((t -= 2) * t * (((s *= (1.525)) + 1) * t + s) + 2) + b; }