vant/packages/switch/src/switch.pcss

@component-namespace o2 {
  @component switch { 
    height: 29px;
    width: 49px;
    display: inline-block;
    border-radius: 16px;
    position: relative;
    border: 1px solid;

    @descendent node {
      width: 27px;
      height: 27px;
      border-radius: 100%;
      background-color: #fff;
      border: .5px solid rgba(0, 0, 0, .1);
      position: absolute;
      box-shadow: 0 3px 1px 0 rgba(0, 0, 0, .05), 0 2px 2px 0 rgba(0, 0, 0, .1), 0 3px 3px 0 rgba(0, 0, 0, .05);
      @when on {
        left: 0;
      }

      @when off {
        right: 0;
      }

    }

    @when on {
      background-color: #44db5e;
      border-color: #44db5e;
    }

    @when off {
      background-color: #fff;
      border-color: rgba(0, 0, 0, .1);
    }

    @when loading {
        /* TODO */
    }

    @when disabled {
      background-color: #f2f2f2;
      border-color: rgba(0, 0, 0, .1);
    }
  }
}