* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html, body {
    width: 100%;
    height: 100%;
    overflow: hidden;
}

body {
    background-image: url('images/background_768x1024_opt.jpg');
    background-size: cover;
    background-position: center;
    background-repeat: no-repeat;
    background-attachment: fixed;
}

.container {
    width: 100%;
    height: 100vh;
}

/* Tablet - Horizontal */
@media screen and (min-width: 768px) and (max-width: 1279px) {
    body {
        background-image: url('images/background_1280x720_opt3.jpg');
    }
}

/* Desktop - Full HD */
@media screen and (min-width: 1280px) {
    body {
        background-image: url('images/background_1920x1080_opt.jpg');
    }
}

/* Orientación portrait en tablets */
@media screen and (min-width: 768px) and (max-width: 1024px) and (orientation: portrait) {
    body {
        background-image: url('images/background_768x1024_opt.jpg');
    }
}

/* Optimización para pantallas retina */
@media screen and (-webkit-min-device-pixel-ratio: 2),
       screen and (min-resolution: 192dpi) {
    body {
        image-rendering: -webkit-optimize-contrast;
        image-rendering: crisp-edges;
    }
}