Animating Linkages with Scratch
Here's a video of TrotBot simulated in Scratch. The embedded simulator can be found on the bottom of this page.
Scratch is made for creating games, so......
Below are the embedded sims, which require Flash to run on this web page. You can also run them on MIT's site where you can download or modify the Scratch code.
To play TrotBot Goalie, click the green flag to start. Then, press the left keyboard arrow to walk left, the right arrow to walk right, "z" to jump left, "x" to jump right.