blockscout/apps/explorer_web/assets/css/components/_sidebar.scss

/* ---------------------------------------------------
    SIDEBAR STYLE
----------------------------------------------------- */
#sidebar  {
  width: 200px;
  background: $navbar-light-color;
  top: 0px;
  z-index: 9999;
  height: 100%;
  position: fixed;

  .sidebar-header {
    background-color: $primary;
    color: $gray-800;
    height: 66px;
    padding: 12px 12px 17px;
    text-align: center;
    box-shadow:0 2px 2px 0 rgba(38,50,56,.16), 0 0 2px 0 rgba(38,50,56,.12);
  }
}

#sidebar .menu-items {
  list-style: none;
  padding: 0.5em 0;
  margin: 0;

  div {
    color: $gray-800;
    padding: 24px 2px 24px 18px;
    font-size: 13px;
    font-weight: normal;
    background-repeat: no-repeat;
    background-position: left 20px center;
    transition: all 0.15s linear;
    cursor: pointer;

    img {
      width: 35px;
      height: 100%;
      margin-right: 5px;
    }

    &:hover {
     background-color: rgba(0, 0, 0, 0.1);
    }

    &:focus {
     outline: none;
    }
  }

}

#sidebar li {
  list-style-type: none;
  padding-left: 5px;
  line-height: 25px;
}

a[data-toggle="collapse"] {
    position: relative;
}

#sidebar--container {
  width: 200px;
  display: none;
}

#pageSubmenu {
  margin-bottom: 5px;
}

/* ---------------------------------------------------
    CONTENT STYLE
----------------------------------------------------- */
#sidebarCollapse {
  display: none;
}


/* ---------------------------------------------------
    MEDIAQUERIES
----------------------------------------------------- */
@media (max-width: 768px) {
    #sidebar--container {
        display: block;
        margin-left: -200px;
        transform: rotateY(90deg);
        height: 100vh;
        position: fixed;
        transition: all 0.6s cubic-bezier(0.945, 0.020, 0.270, 0.665);

        ~ #content {
          position: absolute;
          left: 0;
          right: 0;
          transition: all 0.6s cubic-bezier(0.945, 0.020, 0.270, 0.665);
        }
      }

    #sidebar--container.active {
        margin-left: 0;
        transform: none;
        outline: none;

        ~ #content {
          left: 200px;
          right: -200px;
        }
      }

    #sidebar .menu-items div {
      padding-top: 11px;
    }

    #sidebarCollapse {
      display: block;
      width: 45px;
      height: 66px;
      background-image: none;
      background-color: $primary;
      border-color: transparent !important;
      box-shadow: 0 2px 2px 0 rgba(38,50,56,.16), 0 0 2px 0 rgba(38,50,56,.12);
      outline: none;
    }

    #sidebarCollapse span {
        width: 80%;
        height: 2px;
        margin: 0 auto;
        display: block;
        background: $white;
        transition: all 0.8s;
    }


    #sidebarCollapse span:first-of-type,
    #sidebarCollapse span:nth-of-type(2),
    #sidebarCollapse span:last-of-type {
        transform: none;
        opacity: 1;
        margin: 7px auto;
    }
    #sidebarCollapse.active span {
        transform: none;
        opacity: 1;
        margin: 0 auto;

    }
    #sidebarCollapse.active span:first-of-type {
        transform: rotate(45deg) translate(2px, 2px);
    }
    #sidebarCollapse.active span:nth-of-type(2) {
        opacity: 0;
    }
    #sidebarCollapse.active span:last-of-type {
        transform: rotate(-45deg) translate(1px, -1px);
    }
}