func randomCubic(dc *gg.Context) {
x0, y0 := point()
x1, y1 := point()
x2, y2 := point()
x3, y3 := point()
dc.MoveTo(x0, y0)
dc.CubicTo(x1, y1, x2, y2, x3, y3)
drawCurve(dc)
dc.MoveTo(x0, y0)
dc.LineTo(x1, y1)
dc.LineTo(x2, y2)
dc.LineTo(x3, y3)
drawPoints(dc)
}