#bigDiv{
	width: 900px;
	height: 900px;
	margin: 0 auto;
	border: 2px solid black;
}
/*小div*/
#bigDiv>div{
	width: 20px;
	height: 20px;
	border-radius: 10px;
	float: left;
}
/*蛇头*/
#bigDiv>.red{
	background-color: red;
}
/*蛇身*/
#bigDiv>.saddlebrown{
	background-color: saddlebrown;
}
/*食物*/
#bigDiv>.green{
	background-color: green;
}