`@match`

Choose a value by condition: @match(x = y, #000, #fff) is black on the diagonal and white elsewhere.

Syntax

condition: An expression over the cell variables x, y, i, X, Y, I, z, Z, dx, dy, dr and the others, plus n, nx, ny and N inside a @m sequence.
value: Returned when the condition is true. With several pairs the first true condition wins.
fallback: Returned when no condition is true. Empty if omitted.

Inside $() the same idea is match(condition, value, fallback), with only one pair.

@grid: 5 / 60vmin _1px;
background: @match(i > 12, #e6437d, #000);

@grid: 7 / 60vmin _1px;
background: #000;
color: #fff;
@content: @match(x = y, '✓', '');

Several branches:

@grid: 15 / 60vmin _1px;
background: @match(
  dr < 3, #000,
  dr < 5, #e6437d,
  dr < 7, #ebbf4d,
  #eee
);

Inside a sequence:

@grid: 1 / 60vmin;
background: conic-gradient(
  @m12(@match(n % 2 = 0, #000, #fff) 0 @n(*30deg))
);