Generated by SassMeister.com.

SassMeister-input-HTML.html

<div class="tabs-wrap">
  <nav id="tabs">
    <a href="#" class="tab">
      <span>Tab 1</span>
    </a>
    <a href="#" class="tab">
      <span>Tab 2</span>
    </a>
  </nav>
</div>
<div id="page">
  Lorem Ipsum dolor sit amet ...
</div>

SassMeister-input.scss

// ----
// Sass (v3.4.20)
// Compass (v1.0.3)
// ----

body {
  background-color: #000;
  margin: 0;
  padding: 0;
  font-family: sans-serif;
  font-size: 16px;
}

.tabs-wrap{
  .tab {
    height: 50px;
    width: 150px;
    //border-radius: 15px 15px 0px 0px;
    color:white;
    background-color: #555;
    position: relative;
    top: 10px;
    left: 30px;
    display: inline-block;
    z-index: 2;
    //margin-left:5px;
    &:before {
      height: 50px;
      width: 30px;
      //border-radius: 10px 10px 0px 0px;
      content: "";
      position: absolute;
      left: -15px;
      top: 0px;
      -webkit-transform: skewX(-30deg);
      transform: skewX(-30deg);
      z-index: -1;
      background-color:#555;
    }
    &:after {
      height: 50px;
      width: 30px;
      //border-radius: 10px 10px 0px 0px;
      content: "";
      position: absolute;
      left: 135px;
      top: 0px;
      -webkit-transform: skewX(-30deg);
      transform: skewX(-30deg);
      z-index: -1;
      background-color:#555;
    }
    &:hover {
      color: black;
      background-color: #fff;
      transition: 0.3s ease-out;
      &:before {
        background-color: #fff;
        transition: 0.3s ease-out;
      }
      &:after {
        background-color: #fff;
        transition: 0.3s ease-out;
      }
    }
    &.active{
      color:black !important;
      background-color: white !important;
      &:before {
        background-color: white !important;
      }
      &:after {
        background-color: white !important;
      }
    }
    &:nth-of-type(2) {
      background-color: #555;
      top: 10px;
      left: 56px;
      z-index: 1;
      color: #EEE;
      &:before {
        background-color: #555;
      }
      &:after {
        background-color: #555;
        -webkit-transform: skewX(0deg);
        transform: skewX(0deg);
      }
      &:hover {
        color: black;
        background-color: #fff;
        transition: 0.3s ease-out;
        &:before {
          background-color: #fff;
          transition: 0.3s ease-out;
        }
        &:after {
          background-color: #fff;
          transition: 0.3s ease-out;
        }
      }
    }
  }
  .tabs:last-child{
      -webkit-transform: skewX(0deg);
      transform: skewX(0deg);
    }
  span {
  display: inline-block;
  width: 150px;
  text-align: center;
  height: 50px;
  line-height: 50px;
  z-index: 3;
  }
}

#page {
  background-color: white;
  height: calc(100vh - 120px);
  width: calc(100vw - 61px);
  position: relative;
  top: 10px;
  left: 1px;
  padding: 30px;
}

SassMeister-output.css

body {
  background-color: #000;
  margin: 0;
  padding: 0;
  font-family: sans-serif;
  font-size: 16px;
}

.tabs-wrap .tab {
  height: 50px;
  width: 150px;
  color: white;
  background-color: #555;
  position: relative;
  top: 10px;
  left: 30px;
  display: inline-block;
  z-index: 2;
}
.tabs-wrap .tab:before {
  height: 50px;
  width: 30px;
  content: "";
  position: absolute;
  left: -15px;
  top: 0px;
  -webkit-transform: skewX(-30deg);
  transform: skewX(-30deg);
  z-index: -1;
  background-color: #555;
}
.tabs-wrap .tab:after {
  height: 50px;
  width: 30px;
  content: "";
  position: absolute;
  left: 135px;
  top: 0px;
  -webkit-transform: skewX(-30deg);
  transform: skewX(-30deg);
  z-index: -1;
  background-color: #555;
}
.tabs-wrap .tab:hover {
  color: black;
  background-color: #fff;
  transition: 0.3s ease-out;
}
.tabs-wrap .tab:hover:before {
  background-color: #fff;
  transition: 0.3s ease-out;
}
.tabs-wrap .tab:hover:after {
  background-color: #fff;
  transition: 0.3s ease-out;
}
.tabs-wrap .tab.active {
  color: black !important;
  background-color: white !important;
}
.tabs-wrap .tab.active:before {
  background-color: white !important;
}
.tabs-wrap .tab.active:after {
  background-color: white !important;
}
.tabs-wrap .tab:nth-of-type(2) {
  background-color: #555;
  top: 10px;
  left: 56px;
  z-index: 1;
  color: #EEE;
}
.tabs-wrap .tab:nth-of-type(2):before {
  background-color: #555;
}
.tabs-wrap .tab:nth-of-type(2):after {
  background-color: #555;
  -webkit-transform: skewX(0deg);
  transform: skewX(0deg);
}
.tabs-wrap .tab:nth-of-type(2):hover {
  color: black;
  background-color: #fff;
  transition: 0.3s ease-out;
}
.tabs-wrap .tab:nth-of-type(2):hover:before {
  background-color: #fff;
  transition: 0.3s ease-out;
}
.tabs-wrap .tab:nth-of-type(2):hover:after {
  background-color: #fff;
  transition: 0.3s ease-out;
}
.tabs-wrap .tabs:last-child {
  -webkit-transform: skewX(0deg);
  transform: skewX(0deg);
}
.tabs-wrap span {
  display: inline-block;
  width: 150px;
  text-align: center;
  height: 50px;
  line-height: 50px;
  z-index: 3;
}

#page {
  background-color: white;
  height: calc(100vh - 120px);
  width: calc(100vw - 61px);
  position: relative;
  top: 10px;
  left: 1px;
  padding: 30px;
}

SassMeister-rendered.html

<div class="tabs-wrap">
  <nav id="tabs">
    <a href="#" class="tab">
      <span>Tab 1</span>
    </a>
    <a href="#" class="tab">
      <span>Tab 2</span>
    </a>
  </nav>
</div>
<div id="page">
  Lorem Ipsum dolor sit amet ...
</div>