:root {
    --bg-dark-color: rgb(71,72,75);
}

/* Reset */
*,
*:after,
*:before {
    margin: 0;
    padding: 0;
    -webkit-box-sizing: border-box;
    -moz-box-sizing: border-box;
    box-sizing: border-box;
}

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

body.dark {
    background-color: var(--bg-dark-color);
    display: flex;
    align-items: center;
    justify-content: center;
}