Make some pretty triangles.

triangle.scss

@mixin triangle($size, $color, $direction) {
  width: 0;
  height: 0;

  @if $direction == 'up' {
    border-left: $size solid transparent;
    border-right: $size solid transparent;
    border-bottom: $size solid $color;
  } @elseif $direction == 'down' {
    border-left: $size solid transparent;
    border-right: $size solid transparent;
    border-top: $size solid $color;
  } @elseif $direction == 'left' {
    border-top: $size solid transparent;
    border-bottom: $size solid transparent;
    border-right:$size solid $color;
  } @elseif $direction == 'right' {
    border-top: $size solid transparent;
    border-bottom: $size solid transparent;
    border-left: $size solid $color;
  }
}