Only suitable for modern browsers, naturally.
PHP 7 came out yesterday. Here’s the migration guide if you just want to know what’s new.
Of course, you have to start with the traditional spinning cube. It’s practically the “Hello World!” of 3D animation:
That’s the easy part. The hard part is using equilateral CSS triangles to build a spinning octahedron:
And then pulling together even more trigonometry to build an icosahedron:
Which was, while confusing at times, a surprisingly fun puzzle to solve.