body {
    margin: 0;
    padding: 0;
    background: #795548;
    font-family: 'Rubik', sans-serif;
}

header {
    z-index: 3;
    position: fixed;
    display: flex;
    align-content: center;
    justify-content: center;
    height: 10vh;
    width: 100%;
    background-color: #3E2723;
    box-shadow: 0 2px 5px 0 rgba(0, 0, 0, 0.26);
}

h1 {
    font-family: 'VT323', monospace;
    display: flex;
    justify-content: center;
    align-items: center;
    margin: 0;
    padding: 0;
    color: #ffffff;
    text-align: center;
    font-size: 5vh;
}

.board {
    z-index: 1;
    padding: 40px;
    position: fixed;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -40%);
    border-collapse: collapse;
    width: 70vw;
    height: 70vw;
}

.overlay {
    box-sizing: content-box;
    margin-top: 10vh;
    z-index: 2;
    position: absolute;
    left: 0;
    top: 0;
    right: 0;
    bottom: 0;
    width: 100%;
    height: 90vh;
    background-clip: content-box;
    background-color: rgba(0, 0, 0, 0.5);
}

.overlay-content {
    position: relative;
    display: block;
    margin: auto;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
}

.overlay-content>button {
    display: block;
    margin: auto;
    margin-top: 2vh;
    margin-bottom: 2vh;
    width: 15vw;
    height: 5vh;
    border-radius: 2px;
    font-size: 1.5vw;
    color: #ffffff;
    background-color: #8D6E63;
    border-width: 0;
    overflow: hidden;
    outline: 0;
    box-shadow: 0 1px 4px rgba(0, 0, 0, .6);
}

.overlay-content>h2 {
    padding-left: 10vw;
    padding-right: 10vw;
    display: block;
    margin: auto;
    text-align: center;
    color: #ffffff;
    font-size: 3vh;
}

.cell {
    position: relative;
    box-sizing: border-box;
    width: 33.33%;
    border: 3px solid #ffffff;
}

.cell::before {
    content: "";
    display: block;
    padding-top: 33.33%;
}

.cell#cell_0 {
    border-top: 0;
    border-left: 0;
}

.cell#cell_1 {
    border-top: 0;
}

.cell#cell_2 {
    border-right: 0;
    border-top: 0;
}

.cell#cell_3 {
    border-left: 0;
}

.cell#cell_5 {
    border-right: 0;
}

.cell#cell_6 {
    border-bottom: 0;
    border-left: 0;
}

.cell#cell_7 {
    border-bottom: 0;
}

.cell#cell_8 {
    border-bottom: 0;
    border-right: 0;
}

.cell>div {
    box-sizing: content-box;
    margin: 10%;
    position: absolute;
    top: 0;
    bottom: 0;
    left: 0;
    right: 0;
    background-position: center;
    background-size: cover;
    background-repeat: no-repeat;
}

@media screen and (min-aspect-ratio: 1/1) {
    .board {
        position: fixed;
        top: 50%;
        left: 50%;
        transform: translate(-50%, -40%);
        height: 70vh;
        width: 70vh;
    }
}