The snake robots were inspired by my early work on physically-based computer animation. The two movies below show the results of some of this work. A rudimentary mass-spring systems was used for physical simulation along with an anisotropic friction model that simulated the effect of ventral scales gripping the ground. The snake behavior was controlled by adding lateral offsets to the bending angles. In Her Majesty's Secret Serpent, the snake uses concertina progression (with anisotropic friction) followed by lateral undulation. The final leap off of the cliff also uses a form of concertina progression. .