Lessons learned: 1x1 bricks are a pain. If you're serious about building something of mathematical accuracy, buy a lot of 1x3, 1x4, 1x6, 1x8 and so on bricks. 1x1 bricks will invariably fall off and you truly don't want that.
Color purity is a pain. You can get away with a lot if your viewers' eyes are thrown off by a busy color scheme. The cube/sphere/torus and sphere/cylinder works are random colors and don't suffer too much from it. Granted, the torus was deliberately solid green to make it stand out. I suppose that some amount of solid color building is worth pursuing. Also on this note: the topmost (er, bottommost in the picture) yellow knob was almost unsupported throughout the build. It just sorta worked out that way. And of course, every color change represents a seam, a structural weakness.
This project was a little more brittle than I ever want to attempt again - things were trying to fall off at every turn. The final piece seems adequately sturdy, but I don't want to carry it anywhere.
Looking at the finished product, the lighting on one little piece (at about 1 o'clock, if the sphere were a clock) reminds me of the "Crystal Castles" videogame.
Ow, my back hurts.
No Lego for quite a while, I'm promising myself.