<div id="clock" class="light"> 
 <div class="display"> 
  <div class="digits"> 
   ...数字 
  </div> 
 </div> 
</div> 

<div class="eight"> 
 <span class="d1"></span> 
 <span class="d2"></span> 
 <span class="d3"></span> 
 <span class="d4"></span> 
 <span class="d5"></span> 
 <span class="d6"></span> 
 <span class="d7"></span> 
</div> 

#clock .digits div{ 
 text-align:left; 
 position:relative; 
 width: 28px; 
 height:50px; 
 display:inline-block; 
 margin:0 4px; 
} 
#clock .digits div span{ 
 opacity:0; 
 position:absolute; 
 -webkit-transition:0.25s; 
 -moz-transition:0.25s; 
 transition:0.25s; 
} 
#clock .digits div span:before, 
#clock .digits div span:after{ 
 content:''; 
 position:absolute; 
 width:0; 
 height:0; 
 border:5px solid transparent; 
} 
#clock .digits .d1{   height:5px;width:16px;top:0;left:6px;} 
#clock .digits .d1:before{ border-width:0 5px 5px 0;border-right-color:inherit;left:-5px;} 
#clock .digits .d1:after{ border-width:0 0 5px 5px;border-left-color:inherit;right:-5px;} 
然后，我们将数字span元素对应的dl~d7，根据数字来确定哪根横杠显示或不显示，即设置其opacity的值为1。
/* 0 */ 
#clock .digits div.zero .d1, 
#clock .digits div.zero .d3, 
#clock .digits div.zero .d4, 
#clock .digits div.zero .d5, 
#clock .digits div.zero .d6, 
#clock .digits div.zero .d7{ 
 opacity:1; 
}