A SCSS Flexbox Mixin, including IE10 logic

flexbox.scss

@mixin flex-direction($direction: row) {
  -webkit-flex-direction: $direction;
      -ms-flex-direction: $direction;
          flex-direction: $direction;
}

@mixin flex-wrap($wrap: nowrap) {
  @if $wrap == nowrap {
    -ms-flex-wrap: none;
  }
  @else {
    -ms-flex-wrap: $wrap;
  }
  -webkit-flex-wrap: $wrap;
          flex-wrap: $wrap;
}

@mixin flex-order($order: 0) {
  -ms-flex-order: $order;
  -webkit-order: $order;
      -ms-order: $order;
          order: $order;
}

@mixin justify-content($justify: flex-start) {
  @if $justify == flex-start {
    -ms-flex-pack: start;
  }
  @else if $justify == flex-end {
    -ms-flex-pack: end;
  }
  @elseif $justify == space-between {
    -ms-flex-pack: justify;
  }
  @else {
    -ms-flex-pack: $justify;
  }
  -webkit-justify-content: $justify;
      -ms-justify-content: $justify;
          justify-content: $justify;
}

@mixin align-items($align: auto) {
  @if $align == flex-start {
    -ms-flex-align: start;
  }
  @else if $align == flex-end {
    -ms-flex-align: end;
  }
  @else {
    -ms-flex-align: $align;
  }
  -webkit-align-items: $align;
      -ms-align-items: $align;
          align-items: $align;
}

@mixin align-content($align: auto) {
  @if $align == flex-start {
    -ms-flex-line-pack: start;
  }
  @else if $align == flex-end {
    -ms-flex-line-pack: end;
  }
  @else {
    -ms-flex-line-pack: $align;
  }
  -webkit-align-content: $align;
      -ms-align-content: $align;
          align-content: $align;
}

@mixin align-self($align: auto) {
  @if $align == flex-start {
    -ms-flex-item-align: start;
  }
  @else if $align == flex-end {
    -ms-flex-item-align: end;
  }
  @else {
    -ms-flex-item-align: $align;
  }
  -webkit-align-self: $align;
      -ms-align-self: $align;
          align-self: $align;
}

@mixin flex($value){
  -webkit-box-flex: $value;
  -moz-box-flex: $value;
  -webkit-flex: $value;
  -ms-flex: $value;
  flex: $value;
}

@mixin flex-display($important: false){
  @if ($important) {
    display: -webkit-box!important;
    display: -moz-box!important;
    display: -ms-flexbox!important;
    display: -webkit-flex!important;
    display: flex!important;
  }
  @else {
    display: -webkit-box;
    display: -moz-box;
    display: -ms-flexbox;
    display: -webkit-flex;
    display: flex;
  }
}

It makes use of the correct style properties as IE10's implementation of the flexbox spec at the time. As well as the correct properties where needed, notably the use of start and end instead of the current standard flex-start and flex-end.