Concave Borders

by abhitalks

HTML

<div class="curved">
</div>

CSS

body { background-color: orange; }
.curved {
    width: 400px;
    height: 200px;
    background-color: #ccc;
    border-bottom: 6px solid white;
    border-radius: 0 0 35% 35%;
    position: relative;
}
.curved::before {
    background-color: orange;
    height: 200px;
    width: 40px;
    border-radius: 0 40% 50% 0;
    content: '';
    position: absolute;
    top: 0px; left: 0px;
}

.curved::after{
    background-color: orange;
    height: 200px;
    width: 40px;
    border-radius: 40% 0 0 50%;
    content: '';
    position: absolute;
    top: 0px; right: 0px;
}