Here is a model I made that models bipedal walking as an inverted pendulum. You can edit L to change the length of the legs or theta to change the maximum angle of the legs (i.e. taking bigger or smaller steps). The program will simulate 15 steps and then display an average speed.
https://trinket.io/embed/glowscript/0aaf5aabe8?toggleCode=true
Sean Bartz 