details {
  padding: 1em 0;

  summary {
    cursor: pointer;
    display: block;
  }
}

.no-details {
  details {
    :not(summary) {
      display: none;
    }

    &.open * {
      display: block;
    }

    summary:before {
      content: '► ';
    }

    &.open {
      summary:before {
        content: '▼ ';
      }
    }
  }
}

details {
  padding: 1em 0;

  summary {
    cursor: pointer;
    display: block;
  }
}

.no-details {
  details {
    summary:before {
      content: '► ';
    }

    &.open {
      summary:before {
        content: '▼ ';
      }
    }
  }
}

Delete incorrect CSS rules for no-details mode
Delete incorrect CSS rules for no-details mode

If your browser doesnt support natively details tag, this rules crashes content. And more, this styles dont needed for correct work of this plugin, because content block already have `style='display:none'` rule.
