estilos.css

html {
	background: url("fondo.jpg");
	background-size: 100% 100%;
	width: 100%;
	height: 100%;
}

body {
	margin: 0;
	position: absolute;
	height: 100%;
	width: 100%;
	top: 0;
}

.titulo {
	width: 100%;
	text-align: center;
	font-family: 'Sedgwick Ave Display', cursive;
	font-size: 50px;
}

.titulo p {
	margin: 5px 0 5px 0;
}

.titulo h1 {
	vertical-align: middle;
	padding-top: 200px;
}

nav {
	width: 150px;
	background-color: #000033; 
	border-radius: 0 5px 5px 0;
}

nav ul {
	padding: 0;
}

nav li {
	list-style: none;
}

nav a {
	padding: 1.4045em 1.618em;
	display: block;
	color: white;
	text-decoration: none;
}

nav a:hover {
	background-color: #000080;
}

.select {
	background-color: #000060;
}

.divNav {
	height: 100%;
	position: absolute;
	top: 0;
	left: 0;
	background-color: #00004d;
	font-family: 'Passion One', cursive;
}

.footer-menu {
	display: block;
	font-family: 'Lato', sans-serif;
	font-size: 11px;
	color: white;
	padding: 0 5px 15px 5px;
	position: absolute;
	bottom: 0;
}

.footer-menu * {
	display: block;
}

.arrow {
	position: absolute;
	right: 15px;
	top: 20px;
	cursor: pointer;
	visibility: hidden;
	animation: 5s arrowNext;
	animation-fill-mode: forwards;
	animation-delay: 1s;
}

.arrow img {
	width: 100px;
	height: 75px;
}

.arrow-p {
	display: none;
}

@keyframes arrowNext {
	0% {
		opacity: 0;
	}
	100% {
		visibility: visible;
		opacity: 1;
	}
}

.teoria {
	margin: 25px 150px 0 175px;
}

.ejem-particula {
	width: 100px; 
	height: 100px; 
	position: absolute; 
	border-radius: 50px;
}

.ejem-mov {
	background-color: #0000b3;
	cursor: pointer;
}

.ejem-mov-p {
	background-color: #6666ff;
	cursor: pointer;
}

.ejem-stat {
	background-color: #0000cc;
}

.ejem-contenedor {
	padding-top: 100px;
	width: 100%;
}

.ejem-texto {
	margin: 150px 0 0 100px;
	color: #1a0d00;
	width: 600px;
}

.burbuja {
	padding: 15px;
	border-radius: 5px;
	font-family: 'Lato', sans-serif;
	background-color: #85a3e0;
	color: #1a0d00;
}

.burbuja p {
	margin: 0 0 10px 0;
}

.img-exp {
	width: 484px;
	height: 100px;
}

.numberbox {
	width: 50px;
}

.img-content {
	width: 100%;
	align-items: center;
	display: flex;
	justify-content: center;
}

.img-content img {
	margin: auto;
}

.pregunta {
	margin: 0 100px;
	min-height: 50px;
	vertical-align: middle;
	font-size: 25px;
	display: flex;
	justify-content: center;
    align-content: center;
    flex-direction: column;
}

.respuesta {
	margin: 0 110px;
	background-color: #2a52a2;
	cursor: pointer;
	position: relative;
}

.respuesta:hover {
	background-color: #3466cb;
}

.center {
	display: flex;
	justify-content: center;
    align-content: center;
    flex-direction: column;
}

.ajuste {
	padding-bottom: 60px;
}

.califica {
	width: 50px;
	height: 50px;
	position: absolute;
	bottom: 0;
	left: -50px;
	display: none;
}