html {
    box-sizing: border-box; 
    font-size: 62.5%; /* 1 rem = 10px */    
}
*, *:before, *:after {
    box-sizing: inherit;
}
.contenedor {
    width: min(90%, 120rem);
    margin: 0 auto;
}

.footer {
    background-color: #000;
    padding-bottom: 3rem;
    margin-top: 4rem;
}
