<div>
        <h2>Border 增加</h2>
        <span class="border"></span>
        <span class="border-top"></span>
        <span class="border-right"></span>
        <span class="border-bottom"></span>
        <span class="border-left"></span>
      </div>     
        

      <div class="ex-border-0">
        <h2>Border 減少</h2>
        <span class="border-0"></span>
        <span class="border-top-0"></span>
        <span class="border-right-0"></span>
        <span class="border-bottom-0"></span>
        <span class="border-left-0"></span>
      </div>
          
        

      <div>
        <h2>border 顏色</h2>
        <span class="border border-primary"></span>
        <span class="border border-secondary"></span>
        <span class="border border-success"></span>
        <span class="border border-danger"></span>
        <span class="border border-warning"></span>
        <span class="border border-info"></span>
        <span class="border border-light"></span>
        <span class="border border-dark"></span>
        <span class="border border-white"></span>        
      </div>
          
        

      <div>
        <h2>Border-radius</h2>
        <span class="border border-primary rounded"></span>
        <span class="border border-primary rounded-top"></span>
        <span class="border border-primary rounded-right"></span>
        <span class="border border-primary rounded-bottom"></span>
        <span class="border border-primary rounded-left"></span>
        <span class="border border-primary rounded-circle"></span>
        <span class="border border-primary rounded-0"></span>
      </div>