```css
/* gradient.css — monochrome animated page background */

body {
    min-height: 100vh;

    background: linear-gradient(
        -45deg,
        #050505,
        #111111,
        #242424,
        #080808
    );

    background-size: 400% 400%;

    animation: page-gradient 18s ease infinite;

}

@keyframes page-gradient {
    0% {
        background-position: 0% 50%;
    }

    50% {
        background-position: 100% 50%;
    }

    100% {
        background-position: 0% 50%;
    }
}
```