<!DOCTYPE html>
<style>
#game li{
background: blue;
height: 20px;
list-style: none;
margin: 5px 0;
padding: 0;
}
#game li.active{
background: red;
}
</style>
<div id="game">
<ul>
<li></li>
<li></li>
<li></li>
<li></li>
<li></li>
<li></li>
<li></li>
<li></li>
<li></li>
</ul>
</div>
<script>
document.querySelector('#game ul').onclick = function(event) {
var target = event ? event.target : window.event.srcElement;
if (target.tagName == 'LI')
target.className = 'active';
};
</script>