body {
 text-align: center;
 }
 
 #gameArea {
 background-color: lightblue;
 display: inline-block;
 padding-left: 20px;
 padding-right: 20px;
 
 transition:  background-color 3s ease;
 -webkit-transition: background-color 3s ease;
 }
 
 #startGame {
 margin-top: 20px;
 }
 
 
 
 p > span {
 
 background-color: white;
 margin: 5px;
 padding: 10px;
 border-radius: 5px;
 width: 2.5em;
 height: 2.5em;
 display: inline-block;
 
 text-align: center;
 line-height: 2.5em;
 
 vertical-align: middle;
 }
 
 p > span:empty {
 background-color: lightgrey;
 box-shadow: inset 0 0 10px #444;