$loc: 38%;

$white: #fff;
$color: $white;
$black: #000000;
$dark: lighten($black, 9%);
$bright: darken($white, 5%);
$brighter: darken($bright, 5%);

$background: $black;

.element {
  width: 370px; // nicer w static width
  padding: 8%;
  margin: 10px;
   }

.dark {
  color: $color;
  background: $black;
  @include background-image(linear-gradient(to bottom right, $dark, $dark $loc, #000 $loc, $black));

}

.light {
  color: invert($color);
  background: invert($black);
  @include background-image(linear-gradient(to bottom right, $bright, $bright $loc, $brighter $loc, $brighter ));
}

h2 { margin: 0; }