CSS实现内嵌圆角

HTML

<ul>
    <li class="container">
        <div></div>
    </li>
</ul>

SCSS

body{
  background: #25bdff;
}

.corner{
    content: "";
    width: 20px;
    height: 20px;
    background: #25bdff;
    border-radius: 20px;
    border:5px #ffd958 solid;
    content: "";
    position: absolute;
}

.container{
    border-bottom: 6px solid #c06e32;
    border-radius: 10px;
    width: 352px;
    background: #c06e32;
    position: relative;
    overflow: hidden;
    float: left;
    margin: 0 5px 24px 0;

    &::before{
        @extend .corner;
        left: -15px;
        top: -15px;
    }
    &::after{
        @extend .corner;
        right: -15px;
        top: -15px;
    }
    
    >div{
        background: #fbaf5e;
        border:5px #ffd958 solid;
        border-radius: 10px;
        text-align: center;
        padding: 14px 0 20px;
        height:300px;
    }
}