Generated by SassMeister.com.

SassMeister-input.scss

// ----
// Sass (v3.4.7)
// Compass (v1.0.1)
// ----

$color-link-hover: red;
$white: #fff;

@mixin e($name) {
  @at-root &__#{$name} {
    @content;
  }
}

// (m)odifiers get appended with "--" and the $name
@mixin m($name) {
  @at-root &--#{$name} {
    @content;
  }
}

.tabs-menu { 
  list-style: none;
  margin: 0; 
  margin-bottom: 38px;
  
  display: -webkit-box;
  display: -moz-box;
  display: -ms-flexbox;
  display: -webkit-flex;
  display: flex;
  
  flex-flow: row wrap;
  -webkit-flex-flow: row wrap;
  -moz-flex-flow: row wrap;
  -ms-flex-flow: row wrap;

  //@include flex-flow(row wrap);


  // Tab
  // -------------------------
  @include e(tab) { 
    position: relative;
    display: block;
    height: 45px;
    width: 196px;
    border: 2px solid $color-link-hover;
    padding: 1px 0 0;

    line-height: 45px;
    font-size: 15px;
    font-family: ProximaNovaSemibold;
    color: $color-link-hover;
    text-align: center;
    text-transform: uppercase;

    &:hover {
      background: $color-link-hover;
      color: $white;
    }
    
    @include m(is-active) {
    background: $color-link-hover;
    color: $white;

    // Bars
    &:before {
      border-color: $color-link-hover;
      border-style: solid;
      border-width: 8px;
      content: " ";
      height: 0;
      left: 50%;
      margin-left: -8px;
      margin-top: 0;
      position: absolute;
      top: 48px;
      width: 0;
    }
  }
  }

}

SassMeister-output.css

.tabs-menu {
  list-style: none;
  margin: 0;
  margin-bottom: 38px;
  display: -webkit-box;
  display: -moz-box;
  display: -ms-flexbox;
  display: -webkit-flex;
  display: flex;
  flex-flow: row wrap;
  -webkit-flex-flow: row wrap;
  -moz-flex-flow: row wrap;
  -ms-flex-flow: row wrap;
}
.tabs-menu__tab {
  position: relative;
  display: block;
  height: 45px;
  width: 196px;
  border: 2px solid red;
  padding: 1px 0 0;
  line-height: 45px;
  font-size: 15px;
  font-family: ProximaNovaSemibold;
  color: red;
  text-align: center;
  text-transform: uppercase;
}
.tabs-menu__tab:hover {
  background: red;
  color: #fff;
}
.tabs-menu__tab--is-active {
  background: red;
  color: #fff;
}
.tabs-menu__tab--is-active:before {
  border-color: red;
  border-style: solid;
  border-width: 8px;
  content: " ";
  height: 0;
  left: 50%;
  margin-left: -8px;
  margin-top: 0;
  position: absolute;
  top: 48px;
  width: 0;
}