.header {
  position: fixed;
  width: 100%;
  @include box-shadow(0 2px 3px rgba(0, 0, 0, 0.5));
  color: white;
  height: 2.5em;
  padding-top: 0.45em;
  h1 {
    text-align: center;
    font-size: 1.3em;
    font-weight: normal;
    text-shadow: 0 0 4px rgba(0, 0, 0, 0.4);
  }
}

@mixin header($color) {
  background: $color;
  border-bottom: 1px solid darken($color, 15%);
  @include linear-gradient(lighten($color, 40%), darken($color, 5%));
  @extend .header;
}