body {
    margin: 0;
    font-family: Arial, sans-serif;
}
.cabecera {
    display: flex;          
    flex-direction: row;
    background: linear-gradient(to right, #222, #555);
    padding: 10px 20px;
    color: #fff;
}

.logo img {
    width: 60px;
    height: auto;
}

.menu-principal ul {
    list-style: none;
    margin: 0;
    padding: 0;
    display: flex;         
}

.menu-principal li {
    margin-left: 15px;
}

.menu-principal a {
    color: #fff;
    text-decoration: none;
}

.menu-principal a.activo {
    text-decoration: underline;
}

.contenido {
    padding: 20px;
}

.hero {
    max-width: 1200px;
    width: 100%;
    margin: 0 auto;
}
.texto-bajo-contraste {
color: #333;
    background-color: #f7f7f7;
    padding: 5px 10px;
    border-radius: 4px;
}
.boton-falso {
    margin-top: 15px;
    padding: 10px 20px;
    background-color: #007bff;
    color: #ffffff;
    cursor: pointer;
}
.pie {
    margin-top: 40px;
    padding: 10px 20px;
    background-color: #222;
    color: #fff;
    text-align: center;
}