InOut = function (v)
{
    if ((v *= 2) < 1)
    {
        return 0.5 * v * v * v * v;
    }
    else
    {
        return -0.5 * ((v -= 2) * v * v * v - 2);
    }
}
Quartic ease-in/out.

@function Phaser.Math.Easing.Quartic.InOut
@since 3.0.0

@param {number} v - The value to be tweened.

@return {number} The tweened value.