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

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

header #newgamebt {
    display: block;
    margin: 20px auto;
    width: 100px;
    padding: 10px;
    text-decoration: none;
    background-color: #8f7a66;
    font-family: Arial;
    color: white;
    border-radius: 10px;
}

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

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

#container {
    width: 460px;
    height: 460px;
    margin: 50px auto;
    padding: 20px;
    background-color: #bbada0;
    position: relative;
    border-radius: 10px;
}

.grid-cell {
    width: 100px;
    height: 100px;
    position: absolute;
    background-color: #ccc0b3;
    border-radius: 10px;
}

.number-cell {
    position: absolute;
    font-family: Arial;
    font-weight: bold;
    line-height: 100px;
    font-size: 60px;
    text-align: center;
    border-radius: 6px;
}