JSFiddle - React, Tailwind, and code Playground

HTML

<input type="button" id="add" value="+" title="" style="position: absolute; left: 0px; top: 0px; width: 52px; height: 52px;">

CSS

#add {
	-webkit-box-sizing: content-box;
	-moz-box-sizing: content-box;
	box-sizing: content-box;
	outline: none;
	cursor: pointer;
	padding: 10px;
	overflow: hidden;
	border: none;
	-webkit-border-radius: 50%;
	border-radius: 50%;
	color: rgba(255,255,255,0.9);
	text-align: center;
	background: #1abc9c;
	-webkit-box-shadow: 0 4px 3px 2px rgba(0,0,0,0.2) ;
	box-shadow: 0 4px 3px 2px rgba(0,0,0,0.2) ;
}

#add:active {
	opacity: 0.85;
	-webkit-box-shadow: 2px 2px 2px 0 rgba(0,0,0,0.2) ;
	box-shadow: 2px 2px 2px 0 rgba(0,0,0,0.2) ;
}