Checkerboard Pattern mixin - from L. Verou's book "CSS Secrets", 2015

checkerboard-mixin.scss

@mixin checkerboard($size, $base, $accent: rgba(0,0,0, 0.26)) {
  background: $base;
  background-image: linear-gradient(
      45deg,
      $accent 25%,
      transparent 0,
      transparent 75%, $accent 0
    ),
    linear-gradient(
      45deg,
      $accent 25%, transparent 0,
      transparent 75%, $accent 0);
  background-position: 0 0, $size $size;
  background-size: 2 * size 2 * $size;
  }
}

// use as 
// @include checkerboard(15px, #58am tan);