JSFiddle - React, Tailwind, and code Playground

HTML

<div class="box">
    <div class="circle">
        
    </div>
</div>

CSS

.box
{
    background-color:blue;
    width:450px;
    height:250px;
    
    
}

.circle {
  position:absolute;
  right:0;
    filter: alpha(Opacity=90);
opacity: 0.9;
background-color:red;
	border-radius: 50%;
	width: 250px;
	height: 250px; 
    text-align:center;
   
}