Just move the mouse pointer around to move the leg, and use the arrow keys to flip the direction. Press the space bar to enter walk mode.
This leg is all based on the foot, so you only move the foot, unlike others where you move every point manually. It uses trigonometry, so I tried to make it very simple. It is based on the foot's position, I haven't made it so the hip is a variable yet. If you modify the leg, some variables and some other numbers may need to be changed to match the new leg's characteristics.
