// Stroke contrast
// Ripped off from https://github.com/twbs/bootstrap/commit/c31d52499811d5c68d122db806ce27a112b489bd
@mixin stroke-yiq($color) {
  $r: red($color);
  $g: green($color);
  $b: blue($color);

  $yiq: (($r * 299) + ($g * 587) + ($b * 114)) / 1000;

  @if ($yiq >= 150) {
    stroke: #111;
  } @else {
    stroke: #fff;
  }
}