// Sizing mixin
@mixin size($size) {

  // If only one value is present
  @if length($size) == 1 {

    @if $size == auto{
      width: auto;
      height: auto;
    }
    @else if unitless($size) {
      width: $size + px;
      height: $size + px;
    }
    @else if not(unitless($size)) {
      width: $size;
      height: $size;
    }
  }

  // If both values are present
  @if length($size) == 2 {

    $width: nth($size, 1);
    $height: nth($size, 2);

    @if $width == auto {
      width: $width;
    }
    @else if unitless($width){
      width: $width + px;
    }
    @else if not(unitless($width)) {
      width: $width;
    }

    @if $height == auto{
      height: $height;
    }
    @else if unitless($height) {
      height: $height + px;
    }
    @else if not(unitless($height)) {
      height: $height;
    }
  }
}