header {
    display: block;
    margin: 0 auto;
    margin-top: 4%;
    width: 100%;
    text-align: center;
    position: relative;
}

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

header #newGame {
    display: block;
    margin: 20px auto;
    width: 100px;
    padding: 10px 20px;
    background-color: rgb(204, 38, 38);
    font-family: Arial;
    color: #fff;
    border-radius: 10px;
}

header #newGame:hover {
    background-color: rgb(238, 16, 16);
}

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

header #addScore {
    position: absolute;
}

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

.grid-cell {
    width: 100px;
    height: 100px;
    background-color: rgb(230, 214, 214);
    border-radius: 8px;
    position: absolute;
}

.number-cell {
    width: 100px;
    height: 100px;
    border-radius: 8px;
    font-family: Arial;
    font-weight: bold;
    font-size: 30px;
    line-height: 100px;
    text-align: center;
    position: absolute;
    color: #fff;
}

.overlay {
    width: 100%;
    height: 100%;
    position: fixed;
    top: 0;
    left: 0;
    background-color: rgba(207, 198, 198, 0.5);
    z-index: 9;
    display: none;
}

.prop {
    width: 300px;
    height: 160px;
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    margin: auto;
    background-color: #fff;
    z-index: 10;
    border-radius: 10%;
    text-align: center;
}

.prop h2 {
    margin: 10% auto;
}

.prop a {
    background-color: rgb(36, 39, 226);
    padding: 4% 8%;
    color: #fff;
    border-radius: 4%;
}