> And who didn't do that! :)

Exactly. It's even how I taught myself extremely basic Pascal -- getting my BASIC Life program running in Pascal. With asterisks.

A taught a friend at uni, who was a much better programmer than me, how the algorithm worked. He did a pixel-by-pixel version in machine code, but it was a bit slow on a ZX Spectrum.

So he did exactly the quarter-character-cell version you describe. I wrote the editor in BASIC, and he wrote a machine-code routine that kicked in when told and ran the generations. For extra fun he emitted some of the intermediate state to the border, so the border flashed stripes of colour as it calculated, so you could see it "thinking". Handy for static patterns -- you could see it hadn't crashed.

I've been considering doing a quarter-cell Mandelbrot for about 30Y now. Never got round to it yet.