body {
    margin: 0;
    padding: 0;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    background-image: url('../image/background/4.jpg');
    background-size: cover;
    background-position: center;
    background-repeat: no-repeat;
    background-attachment: fixed;
}

main {
    flex: 1;
}

header, footer {
    background-color: #31667c;
    color: white;
    padding: 5px;
}