.hovertip {
    cursor: pointer;
    position: relative;
}

.hovertip:hover::after {
    position: absolute;
    bottom: -2px;
    padding: 2px;
    color: #000;
    content: attr(hover);
    width: max-content;
    white-space: nowrap;
    background-color: #fdfdb0;
}

.header {
    display: flex;
    align-items: center;
    padding: 8px;
    font-size: 18px;
    text-decoration: underline;
}

.dg {
    margin-left: auto;
    display: block;
}

.dg img {
    display: block;
    height: 50px;
}

.dg img:hover {
    filter: invert();
}

.header ul {
    display: flex;
    justify-content: space-between;
    width: 55%;
    list-style: none;
    margin: 0;
    padding: 0;

    color: #000;
}

.headerimg {
    height: 150px;
    width: 760px;
}

.headerimg img {
    width: 100%;
    height: 100%;
    object-fit: cover;
}

.extra {
    position: sticky;
    top: 80px;

    margin-top: 80px;
    margin-right: 130px;
    margin-left: auto;
    width: calc(37vw);
    height: 300px;
    box-sizing: border-box;

    display: grid;
    grid-template-columns: 1fr 1fr;
    grid-template-rows: 2fr;
    gap: 12px;
}

.about,
.author {
    opacity: 0;
    pointer-events: none;
    box-sizing: border-box;
    border: 1px dashed #ff7208;
    overflow: auto;

    padding: 8px;
}

.about    { grid-column: 1; grid-row: 1; }
.author   { grid-column: 2; grid-row: 1; }

.about.visible,
.author.visible {
    opacity: 1;
    pointer-events: auto;
}