Removed it and other animations when render and animation speed became an issue and I focused on optimizing render speeds. Then I never got around to putting them back in. Like, a webgl version of this could probably have a hundred times more hexagons and you wouldn't lose any FPS. But in SVG, it's weird. Biggest surprise, Chrome is finally slow at something - SVG renders - whereas FireFox blazed right through it.

Then a very polite Canadian kid I met on a minecraft server helped me with it, tracing the fundamental issues (thanks, BubbyMK2!). Apparently using rectangles (svg:rect) is particularly slow in SVG, because it forces a redraw outside its clipping boundary. But if you draw a rectangle as a path, no sweat. Or some such.