Camp T-shirt design
Much like the spirograph applet, but don't have to wait for the figure to draw. Can adjust inner design (both innerinner circle size and innerouter circle size and d1-where is pen in outer circle) and the outer design (both outerinner and outeroutercircle size and d2-where is pen in outer circle). Don't see the circles like you can at http://www.mathplayground.com/Spiromath.html. But you can see both designs at once and adjust colors (background and of each spirograph design). Outer circle having negative size switches it to rotate inside the inner circle.