Mailspring/_sass/_nav.scss

.nav {
  z-index: 10;
  &.index-nav {
    @include animation(fadeIn 2s $ease-in-out-cubic);
    @include keyframes(fadeIn) {
      0% {
        opacity: 0;
      }
      100% {
        opacity: 1;
      }
    }
  }

  overflow: hidden;

  height: 50px;
  line-height: 50px;
  box-shadow: 0 1px 1px rgba(0,0,0,0.35);
  -webkit-user-select:none;
  cursor: pointer;
  position:fixed;
  width:100%;
  background-color:rgba(255,255,255,1);
  a {
    color: inherit;
    &:hover {
      cursor: pointer;
    }
  }
  ul {
    display: inline-block;
    padding:0;
    margin: 0;
    vertical-align: top;
    li {
      list-style-type: none;
      display: inline-block;
      color: rgba(0,0,0,0.7);
      a {
        padding: 15px;
      }
      &:first-child {
        a {
          padding-left: 0;
        }
      }
    }
    li:hover {
      color: rgba(0,0,0,1);
    }
    li.active {
      font-weight: 600;
      color: rgba(0,0,0,1);
    }
  }

  .alt-nav-actions {
    float: right;
    display: block;
  }

  .logo {
    margin-right: 30px;
  }

  .hamburger {display: none;}

  @include transition(height 500ms ease-in-out);

  @media (max-width: 800px) {
    &.open {
      height: 173px;
    }

    .logo {
      display: block;
    }
    .alt-nav-actions {
      float: none;
    }

    .hamburger {
      display: block;
      position: absolute;
      top: 0;
      right: 0;
      padding: 10px 15px;
      z-index: 2;
      hr {
        width: 25px;
        height: 3px;
        border: 0;
        margin: 5px 0;
        padding: 0;
        background: rgba(0,0,0,0.75);
      }
    }
  }
  @media (max-width: 470px) {
    ul.main-nav-actions li a {
      padding: 7px;
      &:first-child {
        padding-left: 0;
      }
    }
  }
  @media (max-width: 420px) {
    &.open {
      height: 273px;
    }
    ul li a {
      padding: 0;
    }
    ul li {
      display: block;
      line-height: 30px;
    }
    ul li .btn {
      margin-top: 13px;
    }
  }
}