.bubble{
	position: absolute;
	width: 50px;
	height: 50px;
	background-image: url("../_img/bubble_sprite_sheet.png");
}
.cur_bubble{
	left: 360px;
	top: 470px;
}
.bubble_0{
	background-position: 0 0;
}
.bubble_1{
	background-position: 0 -50px;
}
.bubble_2{
	background-position: 0 -100px;
}
.bubble_3{
	background-position: 0 -150px;
}