* {box-sizing: border-box;}
html, body {
    height: 100%;
    margin:0;
    padding: 0;
}

header {
    height: 4rem;
}

header, footer {
    padding: .5rem;
    background-color: black;
    background: linear-gradient(to bottom, #4c4c4c 0%,#595959 12%,#666666 25%,#474747 39%,#2c2c2c 50%,#000000 51%,#111111 60%,#2b2b2b 76%,#1c1c1c 91%,#131313 100%); 
    color: white;
}

main {
    padding: .5rem;
}
section {
    padding: .5rem;
    background-color: rgba(255,255,255,0.5);
}

header img, footer img {
    height: 100%;
}

footer {
    height: 3rem;
    position: absolute;
    bottom: 0;
    width: 100%;
}