Thursday's CSS3 bitmaps were clever and fun, but a little counter-HTML5-cultural: the whole point of SVG, Canvas, and so forth, is that vectors are better, because simpler, than bitmaps.

Today's interactive geometric CSS3 shape is just the opposite: far more pixels than pre-rendering could possibly justify, emphatically composed of 2D surfaces, and fully animated in 3D.

It's a folding/unfolding dodecahedron (not in FF/IE):

On to the code:

Because it's a simple shape, the div-organization is too plain to be interesting. 

The CSS is more satisfying -- with each side-pentagon transformed around x, y, and z axes, as dodecahedronity requires:

#dodecahedron.closed #group5 {
	-webkit-transform: rotateZ(-324deg) rotateX(63deg);
	-moz-transform: rotateZ(-324deg) rotateX(63deg);
	transform: rotateZ(-324deg) rotateX(63deg);
}

and each pentagon defined with gratuitously pleasing transparency:

.p2 {
    position: absolute;
    left: 0px;
    top: 0px;
    width: 0;
    height: 0;
    border-bottom: 59px solid #ff0000;
    border-left: 81px solid transparent;
    border-right: 81px solid transparent;
}

The JavaScript is what you might guess after a few seconds' interaction -- but is written efficiently and clearly enough to merit a look.

Worth checking out, as an excellent, direct instantiation of several cool CSS3 elements.