$prefix-for-webkit: true !default;
$prefix-for-mozilla: true !default;
$prefix-for-microsoft: true !default;
$prefix-for-opera: true !default;
$prefix-for-spec: true !default;

@mixin prefixer ($property, $value, $prefixes) {
  @each $prefix in $prefixes {

    @if $prefix == webkit and $prefix-for-webkit == true {
      -webkit-#{$property}: $value;
    }
    @else if $prefix == moz and $prefix-for-mozilla == true {
      -moz-#{$property}: $value;
    }
    @else if $prefix == ms and $prefix-for-microsoft == true {
      -ms-#{$property}: $value;
    }
    @else if $prefix == o and $prefix-for-opera == true {
      -o-#{$property}: $value;
    }
    @else if $prefix == spec and $prefix-for-spec == true {
      #{$property}: $value;
    }
    @else {
      @warn "Unrecognized prefix: #{$prefix}";
    }
  }
}

@mixin box-sizing($type:border-box) {
  @include prefixer(box-sizing, $type, webkit moz ms o spec);
}

@mixin transform($property...) {
  @include prefixer(transform, $property, webkit moz ms o spec);
}

@mixin keyframes($animationName) {
  @-webkit-keyframes #{$animationName} {
    $browser: '-webkit-' !global;
    @content;
  }
  @-moz-keyframes #{$animationName} {
    $browser: '-moz-' !global;
    @content;
  }
  @-ms-keyframes #{$animationName} {
    $browser: '-ms-' !global;
    @content;
  }
  @-o-keyframes #{$animationName} {
    $browser: '-o-' !global;
    @content;
  }
  @keyframes #{$animationName} {
    $browser: '' !global;
    @content;
  }
} $browser: null;