header {
    display: block;
    margin: 0 auto;
    width: 100%;
    text-align: center;
}

header h1 {
    font-family: Arial;
    font-size: 40px;
    font-weight: bold;
    margin: 20px auto;
}

header #newgamebutton {
    display: block;
    margin: 20px auto;

    padding: 10px 10px;
    width: 100px;
    background-color: #8f7a66;
    border-radius: 10px;

    font-family: Arial;
    color: white;
    text-decoration: none;
}

header #newgamebutton:hover {
    background-color: #9f8b77;
}

header p {
    font-family: Arial;
    font-size: 25px;
    margin: 20px auto;
}

.grid-container {
    width: 480px;
    height: 480px;
    padding: 10px;
    background-color: #bbada0;
    border-radius: 10px;

    margin: 20px auto;
    position: relative;
}

.grid-cell {
    width: 100px;
    height: 100px;
    border-radius: 6px;
    background-color: #ccc0b3;

    position: absolute;
}

.number-cell {
    border-radius: 6px;

    font-family: Arial;
    font-weight: bold;
    font-size: 56px;
    line-height: 100px;
    text-align: center;

    position: absolute;
}