Returns the (x, y) tuple of the point that has progressed a proportion
    n along the line defined by the two x, y coordinates.

    Copied from pytweening module.

def getPointOnLine(x1, y1, x2, y2, n):
    """Returns the (x, y) tuple of the point that has progressed a proportion
    n along the line defined by the two x, y coordinates.

    Copied from pytweening module.
    """
    x = ((x2 - x1) * n) + x1
    y = ((y2 - y1) * n) + y1
    return (x, y)