@include b(radio-group) {
  &.is-underline {
    --line-width: 30%;
    --line-height: 2px;
    --line-offset: 2px;

    .el-radio-button__inner {
      background: none;
      border-color: transparent;
      box-shadow: none;

      &::before {
        content: '';
        position: absolute;
        width: 0;
        height: var(--line-height);
        background: var(--primary);
        bottom: var(--line-offset);
        left: 50%;
        transform: translateX(-50%);
        transition: all 0.3s;
      }
    }

    .el-radio-button__orig-radio:checked + .el-radio-button__inner {
      background: none;
      border-color: transparent;
      box-shadow: none;
      color: var(--primary);

      &::before {
        width: var(--line-width);
      }
    }
  }
}