/* reset */
*  {
	-webkit-box-sizing: border-box;
	-moz-box-sizing: border-box;
	-ms-box-sizing: border-box;
	box-sizing: border-box;
	margin: 0;
	padding: 0;
}

html {
	font-size: 5vw;
}

html, body {
	width: 100%;
	margin: 0;
	padding: 0;
}


/* document */
body {
	font-family: "URW Gothic L", "Helvetica", "Arial", sans-serif;
	/* Background source:
	 * http://www.texturex.com/Leather-Textures/black+leather+texture+large+close+up+grain+material+dark+fabric+stock+photo.jpg.php
	 * Free offered by Free Leather Textures */
	background: url('../../media/black-leather-texture.jpg');
}

.display {
	border: 0.2rem solid gray;
	border-radius: 0.5rem;
	background: black;
	padding: 0.5rem;
	width: 100%;
	display: block;
}
.display > output {
	display: block;
	height: 1.5rem;
	margin: 0;
	color: aqua;
}

form {
	width: 100%;
	padding: 0.5rem;
}

fieldset {
	border: none;
	margin: 0;
	font-size: 0;
}
fieldset > button {
	width: 20%;
	margin: 3.3%;
	padding: 2vw;
}
fieldset > button:nth-child(4n) {
	margin-right: 0;
}
fieldset > button:nth-child(4n+1) {
	margin-left: 0;
}

button {
	box-shadow: 0 0 0.5rem black;
	border: none;
	border-radius: 0.5rem;
	text-align: center;
	vertical-align: middle;
	margin: 0;
	font-weight: bold;
	font-size: 1.5rem;
}
output {
	font-size: 1rem;
}


button.number, button.command {
	background: white;
}
button.number:active, button.command:active {
	background: rgb(230, 230, 230);
	box-shadow: inset 0 0 0.5rem black;
}
button.operator {
	box-shadow: 0 0 0.5rem rgb(80,80, 80);
	background: black;
	color: white;
}
button.operator:active {
	background: rgb(60, 60, 60);
	box-shadow: inset 0 0 0.5rem black;
}

#key-c {
	background: red;
	color: white;
}
#key-c:active {
	background: darkred;
}