base-project/admin-ui/src/assets/styles/sidebar.scss

#app {

  .main-container {
    min-height: 100%;
    transition: margin-left .28s;
    margin-left: $base-sidebar-width;
    position: relative;
  }

  .sidebarHide {
    margin-left: 0 !important;
  }

  .sidebar-container {
    -webkit-transition: width .28s;
    transition: width 0.28s;
    width: $base-sidebar-width !important;
    background-color: $base-menu-background;
    height: 100%;
    position: fixed;
    font-size: 0px;
    top: 0;
    bottom: 0;
    left: 0;
    z-index: 1001;
    overflow: hidden;
    text-shadow: .1em .1em 0 #000;



    &.theme-light {
      text-shadow: .1em .1em 0 #FFF;

      li {

        &::before {
          background-color: #FFF5;
        }
      }
    }

    // -webkit-box-shadow: 2px 0 6px rgba(0,21,41,.35);
    // box-shadow: 2px 0 6px rgba(0,21,41,.35);

    &::before {
      content: '';
      position: absolute;
      inset: 0;
      // background-color: red;
      background-image: radial-gradient(circle, var(--noise-color, #FFFFFF06) .5rem, #0000 1rem, #0000 100%);
      background-size: 2rem 2rem;
      filter: url(#WEffectNoiseBgFilter);
      transform: scale(2);
    }

    &.theme-light::before {
      --noise-color: #00000006;
    }

    // reset element-ui css
    .horizontal-collapse-transition {
      transition: 0s width ease-in-out, 0s padding-left ease-in-out, 0s padding-right ease-in-out;
    }

    .scrollbar-wrapper {
      overflow-x: hidden !important;
    }

    .el-scrollbar__bar.is-vertical {
      right: 0px;
    }

    .el-scrollbar {
      height: 100%;
    }

    &.has-logo {
      .el-scrollbar {
        height: calc(100% - 50px);
      }
    }

    .is-horizontal {
      display: none;
    }

    a {
      display: inline-block;
      width: 100%;
      overflow: hidden;
    }

    .svg-icon {
      margin-right: 16px;
    }

    .el-menu {
      border: none;
      height: 100%;
      width: 100% !important;
    }

    .el-menu-item,
    .menu-title {
      overflow: hidden !important;
      text-overflow: ellipsis !important;
      white-space: nowrap !important;
    }

    .el-menu-item .el-menu-tooltip__trigger {
      display: inline-block !important;
    }

    // menu hover
    .sub-menu-title-noDropdown,
    .el-sub-menu__title {
      &:hover {
        background-color: rgba(0, 0, 0, 0.06) !important;
      }
    }

    & .theme-dark .is-active>.el-sub-menu__title {
      color: $base-menu-color-active !important;

    }

    // .el-menu-item.is-active {
    //   --el-menu-active-color: #FFF;
    // }

    & .nest-menu .el-sub-menu>.el-sub-menu__title,
    & .el-sub-menu .el-menu-item {
      min-width: $base-sidebar-width !important;

      &:hover {
        background-color: rgba(0, 0, 0, 0.06) !important;
      }
    }

    & .theme-dark .nest-menu .el-sub-menu>.el-sub-menu__title:not(.is-active),
    & .theme-dark .el-sub-menu .el-menu-item:not(.is-active) {
      background-color: $base-sub-menu-background !important;

      &:hover {
        background-color: $base-sub-menu-hover !important;
      }
    }

    
    .router-link-active.router-link-exact-active {
      position: relative;
      background-color: var(--el-menu-active-color);

      &::before {
        content: '';
        position: absolute;
        inset: 0;
        background-image: linear-gradient(to bottom, #0000 50%, #0003);
      }
      
      &::after {
        content: '';
        position: absolute;
        width: 0;
        height: 0;
        border: solid .5rem #0000;
        
        border-right-color: #f7f7f7;
        top: 50%;
        transform: translateY(-50%);
        right: 0;
      }

      .el-menu-item.is-active {
        position: relative;
        color: var(--my-menu-active-color, #FFF);

        background-color: none !important;

        &:hover {
          background-color: none !important;
        }
      }
    }
  }

  .hideSidebar {
    .sidebar-container {
      width: 54px !important;
    }

    .main-container {
      margin-left: 54px;
    }

    .sub-menu-title-noDropdown {
      padding: 0 !important;
      position: relative;

      .el-tooltip {
        padding: 0 !important;

        .svg-icon {
          margin-left: 20px;
        }
      }
    }

    .el-sub-menu {
      overflow: hidden;

      &>.el-sub-menu__title {
        padding: 0 !important;

        .svg-icon {
          margin-left: 20px;
        }

      }
    }

    .el-menu--collapse {

      .el-sub-menu {
        &>.el-sub-menu__title {
          &>span {
            height: 0;
            width: 0;
            overflow: hidden;
            visibility: hidden;
            display: inline-block;
          }

          &>i {
            height: 0;
            width: 0;
            overflow: hidden;
            visibility: hidden;
            display: inline-block;
          }
        }
      }
    }
  }

  .el-menu--collapse .el-menu .el-sub-menu {
    min-width: $base-sidebar-width !important;
  }

  // mobile responsive
  .mobile {
    .main-container {
      margin-left: 0px;
    }

    .sidebar-container {
      transition: transform .28s;
      width: $base-sidebar-width !important;
    }

    &.hideSidebar {
      .sidebar-container {
        pointer-events: none;
        transition-duration: 0.3s;
        transform: translate3d(-$base-sidebar-width, 0, 0);
      }
    }
  }

  .withoutAnimation {

    .main-container,
    .sidebar-container {
      transition: none;
    }
  }
}

// when menu collapsed
.el-menu--vertical {
  &>.el-menu {
    .svg-icon {
      margin-right: 16px;
    }
  }

  .nest-menu .el-sub-menu>.el-sub-menu__title,
  .el-menu-item {
    &:hover {
      // you can use $sub-menuHover
      background-color: rgba(0, 0, 0, 0.06) !important;
    }
  }

  // the scroll bar appears when the sub-menu is too long
  >.el-menu--popup {
    max-height: 100vh;
    overflow-y: auto;


    &::-webkit-scrollbar-track-piece {
      background: #d3dce6;
    }

    &::-webkit-scrollbar {
      width: 6px;
    }

    &::-webkit-scrollbar-thumb {
      background: #99a9bf;
      border-radius: 20px;
    }
  }



}