body {
    font-family: cursive;
    font-size: 14pt;
    margin: 0;
    padding: 0;
}

h1, p, div {
    text-align: center;
}

#puzzlearea {
    margin: 0 auto;
    display: block;
    width: 400px;
    height: 400px;
    position: relative;
}

#puzzlearea div {
    position: absolute;
    width: 90px;
    height: 90px;
    border: 5px solid #000;
    font-size: 40pt;
    background-image: url("background.jpg");
    background-size: 400px 400px;
}

#puzzlearea > div.movable:hover {
    border-color: red;
    color: red;
}