body {
    text-align: center;
}

body header, body article, body footer {
    display: block;
    margin: 32px auto;
}

.content {
    width: 1024px;
    border-radius: 16px;
    box-shadow: 4px 4px 8px grey;
    padding: 32px;
}

.content .centerAlign h1, .content .centerAlign h2, .content .centerAlign h3, .content .leftAlign h1, .content .leftAlign h2, .content .leftAlign h3 {
    display: inline-block;
    font-weight: bold;
}

.content .centerAlign {
    text-align: center;
}

.content .leftAlign {
    text-align: left;
}

.content .img_illustration {
    display: inline-block;
    text-align: left;
    width: 768px;
}

a {
    text-decoration: none;
    color: lightseagreen;
}

.a_paper, .a_code, .a_video {
    margin-left: 1em;
    margin-right: 1em;
}

.a_paper::before, .a_code::before, .a_video::before {
    font-family: 'Segoe UI Emoji', 'Apple Color Emoji', 'Segoe UISymbol', 'Noto Color Emoji';
    padding-right: 0.5em;
}

.a_paper::before {
    content: '📄';
}

.a_code::before {
    content: '⌨';
}

.a_video::before {
    content: '📽';
}

.a_sub::before {
    content: '　';
}

.row {
    display: grid;
    grid-template-columns: 1fr 1fr;
    grid-gap: 10px;
    width: 100%;
}

.row_3 {
    display: grid;
    grid-template-columns: 1fr 1fr 1fr;
    grid-gap: 10px;
    width: 100%;
}

.row_4 {
    display: grid;
    grid-template-columns: 1fr 1fr 1fr 1fr;
    grid-gap: 10px;
    width: 100%;
}

.row .title, .row_3 .title, .row_4 .title {
    display: flex;
    justify-content: center;
    align-items: center;
}

.row .cell {
    display: flex;
    justify-content: center;
    align-items: center;
    height: 384px;
}

.row_3 .cell {
    display: flex;
    justify-content: center;
    align-items: center;
    height: 256px;
}

.row_4 .cell {
    display: flex;
    justify-content: center;
    align-items: center;
    height: 192px;
}

.row .cell video, .row_3 .cell video, .row_4 .cell video {
    width: 100%;
    height: 100%;
    object-fit: contain;
    background-color: black;
}

.row .cell img, .row_3 .cell img, .row_4 .cell img {
    width: 100%;
    height: 100%;
}