bluespec-docs/sass/_header.scss

@mixin menu-icon() {
  @keyframes clickfirst {
    0% {
      transform: translateY(6px) rotate(0deg);

    }

    100% {
      transform: translateY(0) rotate(45deg);
    }
  }

  @keyframes clickmid {
    0% {
      opacity: 1;
    }

    100% {
      opacity: 0;
    }
  }

  @keyframes clicklast {
    0% {
      transform: translateY(-6px) rotate(0deg);
    }

    100% {
      transform: translateY(0) rotate(-45deg);
    }
  }

  @keyframes outfirst {
    0% {
      transform: translateY(0) rotate(-45deg);
    }

    100% {
      transform: translateY(-6px) rotate(0deg);
    }
  }

  @keyframes outmid {
    0% {
      opacity: 0;
    }

    100% {
      opacity: 1;
    }
  }

  @keyframes outlast {
    0% {
      transform: translateY(0) rotate(45deg);
    }

    100% {
      transform: translateY(6px) rotate(0deg);
    }
  }

  span {
    position: absolute;
    /* fallback for browsers which still doesn't support for `calc()` */
    left: 15px;
    top: 25px;
    left: calc((100% - 20px) / 2);
    top: calc((100% - 1px) / 2);
    width: 20px;
    height: 2px;
    background-color: rgba(0, 0, 0, 0.5);

    &:nth-child(1) {
      transform: translateY(6px) rotate(0deg);
    }

    &:nth-child(3) {
      transform: translateY(-6px) rotate(0deg);
    }
  }

  &.icon-click {
    span:nth-child(1) {
      animation-duration: 0.5s;
      animation-fill-mode: both;
      animation-name: clickfirst;
    }

    span:nth-child(2) {
      animation-duration: 0.2s;
      animation-fill-mode: both;
      animation-name: clickmid;
    }

    span:nth-child(3) {
      animation-duration: 0.5s;
      animation-fill-mode: both;
      animation-name: clicklast;
    }
  }

  &.icon-out {
    span:nth-child(1) {
      animation-duration: 0.5s;
      animation-fill-mode: both;
      animation-name: outfirst;
    }

    span:nth-child(2) {
      animation-duration: 0.2s;
      animation-fill-mode: both;
      animation-name: outmid;
    }

    span:nth-child(3) {
      animation-duration: 0.5s;
      animation-fill-mode: both;
      animation-name: outlast;
    }
  }
}

.page__header {
  height: 50px;

  .menu-icon {
    height: 50px;
    width: 50px;
    font-size: 24px;
    text-align: center;
    float: left;
    position: relative;
    transition: background .5s;
    cursor: pointer;

    @include menu-icon();

    &:hover {
      span {
        background-color: black;
      }
    }
  }

  .search-icon {
    height: 50px;
    width: 50px;
    display: inline-block;
    text-align: center;
    line-height: 50px;
    color: rgba(0, 0, 0, 0.5);
    cursor: pointer;
    font-size: 2rem;

    &:hover {
      color: black
    }
  }
}