A bit of 3D.

Quite a lot of arbitrariness in there, though.
Bigger and shinier.

And slightly less arbitrary.
Attempt at different ways to calc and draw

update_fields is quite direction-biased, so I'm trying out a version
that gets some energy from diagonally-adjacent grid points.

Along similar lines, I wanted to see if using TRAINGLE_FAN was better
than TRAINGLE_STRIP.