unescaped vs. escaped id and class selectors

dabblet.css

/**
 * unescaped vs. escaped id and class selectors
 */

div
{
	background: red;
	display: inline-block;
	height: 10em;
	width: 10em;
	padding: 1em;
}

#0 { background: green }
.0 { background: green }
#\31 { background: green }
.\31 { background: green }

dabblet.html

<div id="0">unescaped id selector</div>
<div class ="0">unescaped class selector</div>
<div id="1">escaped id selector</div>
<div class="1">escaped class selector</div>

settings.json

{"view":"separate","fontsize":"100","seethrough":"","prefixfree":"1","page":"all"}