Spirograph
A Spirograph is a curve formed by rolling a circle inside or outside of another circle. If the radius of fixed circle is R, the radius of moving circle is r, and the offset of the pen point in the moving circle is O, then the resulting curve is defined by:
x = (R+r)*cos(t) - O*cos(((R+r)/r)*t)
y = (R+r)*sin(t) - O*sin(((R+r)/r)*t)
(moving circle outside the fixed circle)
