Learning

The algorithm uses tens of parameters for each gait. In short it uses inverse kinematics to create a mapping between joint angles and foot contacts. Design the trajectory of one leg then collaborate all four legs. Save the angles as animation frames and play it on Nybble. Imagine Nybble as a cheap electric keyboard compared with an expensive piano. It's up to you to play any melody on it.

When developing, I programed across different languages for my convenience. Being a short program, the physics simulation was done in my mind. Most of the tuning depends on my intuition and experience. It still takes several hours to fine tune one gait.

I hope people in serious robotics could teach us the right/professional way to generate gaits.

There are a lot of popular simulators, such as Webot. I haven't got a chance to learn them though.