:root {
    --t-bg: rgb(201, 201, 226);
}

body {
    height: 100vh;
    margin: 0;
    display: flex;
    flex-direction: column;
}

footer {
    margin-top: auto;
}

/* sample */
header, footer {
    background-color: var(--t-bg);
    padding: 10px;
}