JSFiddle - React, Tailwind, and code Playground

HTML

<div id="box"></div>

CSS

#box{
    background-color: #00F;
    width: 7em;
    height: 7em;
    margin: 40px auto;
              
    /*          left  top  Blur  size  color, left   top blur  size color */
    box-shadow: 10px  0    6px   -2px  #F00 , -10px  0   6px   -2px white
        ;
    
    -webkit-box-shadow: 10px 0 6px -2px #F00, -10px 0 6px -2px #F00;
}