header {
    position: absolute;
    top: 0;
    left: 0;
    padding: 0 100px;
    width: 100%;
    box-sizing: border-box;
    background: #333;
  }
  
  header .logo {
    color: #fff;
    height: 50px;
    line-height: 50px;
    font-size: 24px;
    float: left;
    font-weight: bold;
  }
  
  header nav {
    float: right;
  }
  
  header nav ul {
    margin: 0;
    padding: 0;
    display: flex;
  }
  
  header nav ul li {
    list-style: none;
    position: relative;
  }
  
  header nav ul li.sub-menu:before {
    content: '\f078';
    font-family: fontAwesome;
    position: absolute;
    line-height: 50px;
    color: #fff;
    right: 1px;
  }
  
  header nav ul li.active.sub-menu:before {
    content: '\f077';
  }
  
  header nav ul li ul {
    position: absolute;
    left: 0;
    background: #333;
    display: none
  }
  
  header nav ul li.active ul {
    /* use li: hover instead */
    display: block;
  }
  
  header nav ul li ul li {
    display: block;
    width: 200px;
  }
  
  header nav ul li a {
    height: 50px;
    line-height: 50px;
    padding: 0 20px;
    color: #fff;
    text-decoration: none;
    display: block;
  }
  
  header nav ul li a:hover {
    color: #fff;
    background: #2196f3;
  }
  
  header nav ul li a.active {
    background: #2196f3;
  }
  
  .menu-toggle {
    color: #fff;
    float: right;
    line-height: 50px;
    font-size: 24px;
    cursor: pointer;
    display: none
  }
  
  @media (max-width: 1300px) {
    header {
      padding: 0 20px;
    }
    .menu-toggle {
      display: block;
    }
    header nav {
      /* use display none or left:-100% to hide the nav  */
      /* display: none; */
      position: absolute;
      top: 50px;
      left: -100%;
      width: 100%;
      height: calc(100vh - 50px);
      background: #333;
      transition: 0.5s;
    }
    header nav.active {
      left: 0;
    }
    header nav ul {
      display: block;
      text-align: center;
    }
    header nav ul li a {
      border-bottom: 0.9px solid rgba(0, 0, 0, .2);
    }
    header nav ul li.active ul {
      position: relative;
      background: #003e6f;
    }
    header nav ul li ul li {
      width: 100%;
    }
  }