A Single Div
The thing I'm always surprised about with these sort of CSS hacks: they don't lag my browser. Like, at all. Even the animated ones! Which is really surprising when you compare them to literally any other way these illustrations could have been created. A sufficient mess of procedural Javascript to render the same designs would lag horribly. The equivalent Flash would make the browser choppy as all hell. As would a Java applet, if those were even still around. (SVG might not, but for the SVG to animate you'd need to use... CSS.)Is CSS effectively "free", or is this just not a complex-enough example to start to see problems?