body {
	background-image: url("tu-imagen.jpg");
	background-size: cover;
	background-position: center center;
	background-repeat: no-repeat;
	height: 100vh;
	margin: 0;
	padding: 0;
}

.container {
	max-width: 500px;
	margin: 0 auto;
	padding: 20px;
	box-shadow: 0 0 10px rgba(0,0,0,.1);
	background-color: rgba(0, 0, 0, 0.8);
	text-align: center;
}

h1 {
	margin-top: 0;
}

.form-group {
	margin-bottom: 20px;
}

label {
	display: block;
}

input[type="range"] {
	width:100%;
}

#length-value {
	font-size: 1.5em;
	margin-left: 10px;
}

input[type="text"] {
	width: 100%;
	padding: 10px;
	font-size: 1.2em;
	border: 2px solid #ccc;
	border-radius: 5px;
}

button {
	margin-top: 10px;
	padding: 10px;
	font-size: 1.2em;
	background-color: #4CAF50;
	color: white;
	border: none;
	border-radius: 5px;
	cursor: pointer;
	transition: background-color .2s;
}

button:hover {
	background-color: #3E8E41;
}

#generate {
	background-color: #666;
}

.container * {
	color: white;
}

#password {
	color: black;
}

@media only screen and (max-width: 600px) {
	.container {
		max-width: 100%;
	}
}