I found it was easier to learn the concepts these writers cover by building my own examples using a common set of classes. Under the hood, the framework describes classes like "Agent", "Sensor", and "Walker" and allows you to easily attach behaviors like "followMouse" or "flock". By creating instances of these classes and adjusting their properties, you can create natural looking systems.
All the simulations are animated using DOM rendering. There is no HTML5 Canvas or Flash involved. All modern browsers have been tested. If you see any differences, it's likely in the CSS. If not, let me know!
Please check out the demos.