Code for implementing bubble boxes using pseudo elements in CSS3 (before, after)

<div class="wrap"></div>

.wrap{
            position: relative;            
            width: 600px;            
            height: 400px;            
            border: 10px solid #3377aa;            
            border-radius: 20px;        
    }
.wrap::before{
            position: absolute;            
            content: '';            
            width: 0;            
            height: 0;            
            border-width: 40px 20px;  
            /*上下、左右的border值*/
            border-style: solid;            
            border-color: #3377aa transparent transparent;
            /*只设置上面border的颜色，左右和下面都设置为透明，会出现一个倒三角*/
            bottom: -80px; 
            /*以下给三角形定位，使其处于底部居中处*/
            left: 50%;            
            margin-left: -20px; 
        }

.wrap::before{
            position: absolute;            
            content: '';            
            width: 0;            
            height: 0;            
            border-width: 40px 20px;            
            border-style: solid;            
            border-color: #3377aa transparent transparent;            
            bottom: -80px;            
            left: 50%;            
            margin-left: -20px;        
        }
.wrap::after{            
                position: absolute;            
                content: '';            
                width: 0;            
                height: 0;            
                border-width: 40px 20px;            
                border-style: solid;            
                border-color: #fff transparent transparent;
                /*白色的倒三角*/
            bottom: -60px; 
            /*位置和往上一些*/
            left: 50%;            
            margin-left: -20px;        
         }

        .wrap::before,        
        .wrap::after{
                    position: absolute;            
                    content: '';            
                    width: 0;            
                    height: 0;            
                    border-width: 40px 20px;            
                    border-style: solid;            
                    border-color: #3377aa transparent transparent;            
                    bottom: -80px;            
                    left: 50%;            
                    margin-left: -20px;        
                }
        .wrap::after{
                    border-color: #fff transparent transparent;            
                    bottom: -60px;       
               }