radial diamond / triangles

aspect-ratio: 1 / 1; /* ? */
@grid: 1 / 100vmin;
@content: @pattern(
  grid: 48;
  size: sin(4*log(dr) - 2t - da);
  fill: match((x - 1) & (y - 1), #000, #fff);
  shape: diamond;
);