html {
    height: 100%;
}

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

main {
    display: flex;
    
    height: 0;
    
    flex-grow: 1;
}

section {
    flex-grow: 1;
}