/* estilo */

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

body {
    background-image: url("../Imagenes/pub.png");
    background-repeat: no-repeat;
    background-position: center center;
    background-size: contain;   /* 👈 clave */
    background-color: #cccccc;
}