ㄧ.Forms:核取方塊與選項按鈕(自定義)
<body data-spy="scroll" data-target="#nav-demo">
  <div class="component" id="demo" style="height: 300vh">
    <div class="custom-control custom-checkbox">
      <input type="checkbox" class="custom-control-input" id="customCheck1">
      <label class="custom-control-label" for="customCheck1">
      A
      </label>
    </div>
    <div class="custom-control custom-radio">
      <input type="radio" class="custom-control-input" name="radio" id="custom-radio1">
      <label class="custom-control-label" for="custom-radio1">
      A
      </label>
    </div>
    <div class="custom-control custom-radio">
      <input type="radio" class="custom-control-input" name="radio" id="custom-radio2">
      <label class="custom-control-label" for="custom-radio2">
      B
      </label>
    </div>
    
  </div>
</body>
.demo.component{
  padding: 50px;
}
重點: