JSFiddle - React, Tailwind, and code Playground

HTML

<div class="menu"></div>
<div class="div1"></div>
<div class="div2"></div>

CSS

.menu 
{
    width:100%;
    background-color:red;
    height:100px;
    position:fixed;
    z-index:99;
    top:0px;
}
.div1 
{
    width:100%;
    background-color:green;
    height:200px;
    top:100px;
    position:relative;
}
.div2 
{
    width:100%;
    background-color:black;
    height:200px;
    position:relative;
    opacity:0.5;
    

}