Here are a few little programs I wrote up on Khan Academy's "learn to program in JavaScript" site that let you draw on a plane by left-clicking and then translate it by right-clicking. The planes are the real projective plane, the Poincare disk, and the Klein-Beltrami disk, respectively: https://www.khanacademy.org/cs/rp/6016720262135808 https://www.khanacademy.org/cs/hyperbolic-poincar-disk/6049095859830784 https://www.khanacademy.org/cs/hyperbolic-beltrami-klein-disk/50893623881891... -- Mike Stay - metaweta@gmail.com http://www.cs.auckland.ac.nz/~mike http://reperiendi.wordpress.com