Generated by SassMeister.com.

SassMeister-input.scss

// ----
// libsass (v3.2.5)
// ----

// Grid settings
$grid-gutter-width: 8px !default;
$grid-columns: 12 !default;
$breakpoints: (xs: 320, sm: 768, md: 1024, lg: 1440);

%clearfix {
    &:before,
    &:after {
        content: ' ';
        display: table;
    }

    &:after {
        clear: both;
    }
}

%container-fluid {
    @extend %clearfix;
    padding-left: ($grid-gutter-width / 2);
    padding-right: ($grid-gutter-width / 2);
    margin: 0 auto;
    max-width: map-get($breakpoints, 'lg');
    @media (min-width: map-get($breakpoints, 'xs')) {
        padding: 0 4px;
    }
    @media (min-width: map-get($breakpoints, 'sm')) {
        padding: 0 10px;
    }
}

%row {
    @extend %clearfix;
    margin-left: ($grid-gutter-width / -2);
    margin-right: ($grid-gutter-width / -2);
}

@mixin make-row($gutter: $grid-gutter-width) {
    @extend %clearfix;
    margin-left: ($gutter / -2);
    margin-right: ($gutter / -2);
}

@mixin make-grid-columns($i: 1, $list: "%col-xs-#{$i}, %col-sm-#{$i}, %col-md-#{$i}, %col-lg-#{$i}") {
    @for $i from (1 + 1) through $grid-columns {
        $list: "#{$list}, %col-xs-#{$i}, %col-sm-#{$i}, %col-md-#{$i}, %col-lg-#{$i}";
    }

    #{$list} {
        position: relative;
        min-height: 1px;
        padding-left: ($grid-gutter-width / 2);
        padding-right: ($grid-gutter-width / 2);
    }
}

@mixin float-grid-columns($class, $i: 1, $list: "%col-#{$class}-#{$i}") {
    @for $i from (1 + 1) through $grid-columns {
        $list: "#{$list}, %col-#{$class}-#{$i}";
    }

    #{$list} {
        float: left;
    }
}

@mixin calc-grid-column($index, $class, $type) {
    @if ($type == width) and ($index > 0) {
        %col-#{$class}-#{$index} {
            width: percentage(($index / $grid-columns));
        }
    }
    @if ($type == push) and ($index > 0) {
        %col-#{$class}-push-#{$index} {
            left: percentage(($index / $grid-columns));
        }
    }
    @if ($type == push) and ($index == 0) {
        %col-#{$class}-push-0 {
            left: auto;
        }
    }
    @if ($type == pull) and ($index > 0) {
        %col-#{$class}-pull-#{$index} {
            right: percentage(($index / $grid-columns));
        }
    }
    @if ($type == pull) and ($index == 0) {
        %col-#{$class}-pull-0 {
            right: auto;
        }
    }
    @if ($type == offset) {
        %col-#{$class}-offset-#{$index} {
            margin-left: percentage(($index / $grid-columns));
        }
    }
}

@mixin loop-grid-columns($columns, $class, $type) {
    @for $i from 0 through $columns {
        @include calc-grid-column($i, $class, $type);
    }
}

@mixin make-grid($class) {
    @include float-grid-columns($class);
    @include loop-grid-columns($grid-columns, $class, width);
    @include loop-grid-columns($grid-columns, $class, pull);
    @include loop-grid-columns($grid-columns, $class, push);
    @include loop-grid-columns($grid-columns, $class, offset);
}

// genrate grid
@include make-grid-columns;
@each $key, $value in $breakpoints {
  @media (min-width: $value+px) {
    @include make-grid($key);
  }
}

// css
.cart {
  @extend %col-xs-1;
  @extend %col-md-3;
  @extend %col-sm-3;
}

SassMeister-output.css

.cart, .cart, .cart {
  position: relative;
  min-height: 1px;
  padding-left: 4px;
  padding-right: 4px;
}

@media (min-width: 320px) {
  .cart {
    float: left;
  }
  .cart {
    width: 8.33333%;
  }
}

@media (min-width: 768px) {
  .cart {
    float: left;
  }
  .cart {
    width: 25%;
  }
}

@media (min-width: 1024px) {
  .cart {
    float: left;
  }
  .cart {
    width: 25%;
  }
}