css使用背景图自定义radio和checkbox的样式

input {    
    appearance: none;    
    -webkit-appearance: none;    
    width: 14px;    
    height: 14px;    
    vertical-align: middle;    
    background: url("../assets/images/3/not-select.png") no-repeat;    
    background-size: cover;    
    &:checked {       
     background: url("../assets/images/3/select.png") no-repeat;      
     background-size: cover;     
    }
}