JSFiddle - React, Tailwind, and code Playground
by jcubed111
HTML
<div class="middle"></div>
<div class="extender"></div>
CSS
.middle{
width: 200px;
height: 200px;
background: #444;
position: absolute;
left: 100px;
top: 100px;
border-bottom-left-radius: 100px;
border-top-right-radius: 100px;
}
.extender{
width: 500px;
background: #444;
height: 200px;
transform-origin: 100px 100px;
position: absolute;
left: 100px;
top: 100px;
transition: transform 0.2s ease-in-out, border-radius 0.2s ease-in-out;
border-top-left-radius: 100px;
border-bottom-left-radius: 100px;
border-top-right-radius: 100px;
}
.extender:hover{
transform: rotate(90deg);
border-top-right-radius: 0px;
border-bottom-right-radius: 100px;
}