CSS3如何实现关闭按钮

/* basic style */
.close {    /* still bad on picking color */
    background: orange;    
    color: red;    /* make a round button */
    border-radius: 12px;    /* center text */
    line-height: 20px;    
    text-align: center;    
    height: 20px;    
    width: 20px;    
    font-size: 18px;    
    padding: 1px;
    }/* use cross as close button */
.close::before {    
    content: "\2716";
    }
    /* place the button on top-right */
.close {    
    top: -10px;    
    right: -10px;    
    position: absolute;
    }

<div style="height: 100px; width: 100px; border: 1px solid black; position: relative;">
    <span class="close"></span>
</div>