def easeInOutQuad(n):
    """A quadratic tween function that accelerates, reaches the midpoint, and then decelerates.

    Args:
      n (float): The time progress, starting at 0.0 and ending at 1.0.

    Returns:
      (float) The line progress, starting at 0.0 and ending at 1.0. Suitable for passing to getPointOnLine().
    """
    _checkRange(n)
    if n < 0.5:
        return 2 * n**2
    else:
        n = n * 2 - 1
        return -0.5 * (n*(n-2) - 1)