html, body {
  height: 100%;
  margin: 0px;
}

#arena {
  background-image: url("arena.png");
  background-size: 100% 100%;
  margin: 0px;
  width: 100%;
  height: 100%;
  overflow: hidden;
}

h1 { 
	font-family: 'PressStart2P', 'Georgia', serif; 
}

h4 { 
	font-family: 'PressStart2P', 'Georgia', serif; 
}

.sprite {
  background-image: url("sprites.png");
  width: 128px;
  height: 192px;
}

.control {
	margin: 32px;
	width: 64px;
	height: 64px;
	transform: scale(1.25); /* 放大2倍 */
}

#controls-left {
  position: absolute;
  left: 0; bottom: 0;
}

#controls-right {
  position: absolute;
  right: 0; bottom: 0;
}

#score {
  position: absolute;
  z-index: 1000;
  left: 50%;
  top: 5%;
  color: White;
  transform: translate(-50%, 0%);
}

#copyright {
  position: absolute;
  z-index: 1000;
  left: 50%;
  top: 95%;
  color: White;
  transform: translate(-50%, 0%);
}

#ball {
	position: absolute;
	width: 64px;
	height: 64px;
	background-position: 0px -128px;
	left: 50%;
	top: 50%;
	visibility: hidden;
	transform: scale(1.5625); /* 放大2倍 */
}

#bt_stop {
  background-position: 0px 0px;
}

#bt_pause {
  background-position: 0px -64px;
}

#bt_start_l1 {
  background-position: -64px 0px;
}

#bt_start_l2 {
  background-position: -64px -64px;
}

#bt_start_l3 {
  background-position: -64px -128px;
}