Stepwising - Stepwising combines the old Stepwise program with Driving in Circles. Check out Kepler's laws of planetary motion, search for solutions to the 3-body problem, or try to drive a rocket powered car around a frictionless circular track of ice. (upper school level) New version 1.1.1 (11/26/2017).
Celestial Dances - explore the orbits and relative motions of the sun, planets, and moons. Discover some surprisingly beautiful relationships. Based on ideas presented in A Little Book of Coincidence by John Martineau. New Version 2.0 (4/30/2018) includes a solar system of exoplanets orbiting the red dwarf star TRAPPIST-1. (middle and upper school level)