header {
    display: block;
    margin: 0 auto;
    width: 500px;
    text-align: center;
}

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

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

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

    font-family: Arial;
    color: white;

    border-radius: 10px;

    text-decoration: none;
}

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

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

#grid-container {
    width: 500px;
    height: 500px;

    margin: 50px auto;
    background-color: #bbada0;

    border-radius: 10px;
    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: 60px;
    line-height: 100px;
    text-align: center;

    position: absolute;
}

.gameover {
    display: block;
    margin: 0 auto;
    width: 500px;
    text-align: center;
    vertical-align: middle;

    position: absolute;
}

.gameover p {
    font-family: Arial;
    font-size: 50px;
    color: white;
    margin: 20px auto;

    margin-top: 150px;
}

.gameover span {
    font-family: Arial;
    font-size: 50px;
    color: white;
    margin: 20px auto;
}

#restartgamebutton {
    display: block;
    margin: 20px auto;

    width: 180px;
    padding: 10px 10px;
    background-color: #8f7a66;

    font-family: Arial;
    font-size: 30px;
    color: white;

    border-radius: 10px;

    text-decoration: none;
}

#restartgamebutton:hover {
    background-color: #9f8b77;
}