@mixin center($position) {
  position: absolute;

  @if $position == 'v' {
    top: 50%;
    -webkit-transform: translateY(-50%);
    -ms-transform: translateY(-50%);
    transform: translateY(-50%);
  }
  @else if $position == 'h' {
    left: 50%;
    -webkit-transform: translateX(-50%);
    -ms-transform: translateX(-50%);
    transform: translate(-50%);
  }
  @else if $position == 'b' {
    top: 50%;
    left: 50%;
    -webkit-transform: translate(-50%, -50%);
    -ms-transform: translate(-50%, -50%);
    transform: translate(-50%, -50%);
  }
}