#zero {
  		width:400px;
  		height:500px;
  		border: 1px solid black;
	}

	.f1 {
		width: 0px;
		height: 350px;
		z-index: 10;
		position: absolute;
		left: 280px;
		top: 100px;
		transform: rotate(20deg);
		border: 3px solid black;
	}

	.f2 {
		width: 0px;
		height: 100px;
		z-index: 20;
		position: absolute;
		left: 280px;
		top: 40px;
		transform: rotate(100deg);
		border: 3px solid black;
	}

	.f3 {
		width: 0px;
		height: 350px;
		z-index: 10;
		position: absolute;
		left: 160px;
		top: 100px;
		transform: rotate(20deg);
		border: 3px solid black;
	}

	.f4 {
		width: 0px;
		height: 100px;
		z-index: 20;
		position: absolute;
		left: 160px;
		top: 400px;
		transform: rotate(100deg);
		border: 3px solid black;
	}

	pre code {
  		background-color: #eee;
  		border: 1px solid #999;
  		display: block;
  		padding: 20px;
  		width:400px;
	}