小练习

#aa{    
                width: 0px;    
                height:0px;
                border-top:  100px solid blue;
                border-left: 100px solid transparent;
                border-right: 100px solid transparent;
                border-bottom: 100px solid transparent;
            }
    
            .bb{
                width: 100px;
                height: 100px;
                border: 3px solid blue;
                border-top: 3px solid transparent;
                border-right: 3px solid transparent;
                transform: rotate(45deg);
                margin-left: 100px;
            }