ferris

Once upon a time there was a display terminal called the General Turtle 2500, with a very early implementation of vector graphics.  It was used to support a version of Logo that included a SPIN command that could give a turtle an angular speed.  Recently Brian Silverman, whose hobby is programming simulations of ancient computers, wrote a 2500 simulator and revived its Logo.  He suggested that no other programming environment could do SPIN.  I said Snap! could do it using nested sprites, and he challenged me to recreate this old 2500 demo program.

Without the circle of lights, the spokes pointing downward appear to be longer than the ones pointing upward, because all the cars are below the endpoints of the spokes.