/*
|--------------------------------------------------------------------------
| Three-page book
|--------------------------------------------------------------------------
|
| Geometry, opening/closing animation, three-page desktop layout and mobile
| book states. Three-page-specific refinements live here so the sectional CSS
| files can stay focused on their own content.
|
*/

.site-shell {
    grid-template-rows: auto auto;
    align-content: center;
}

.site-stage {
    width: min(100%, 1440px);
}

.book-scene {
    --page-width: clamp(22rem, 29vw, 28rem);
    --book-height: clamp(42rem, 75vh, 48rem);
    width: calc(var(--page-width) * 3);
    height: var(--book-height);
    perspective: 3000px;
    perspective-origin: center;
}

.book {
    position: relative;
    width: 100%;
    height: 100%;
    transform: none;
    transform-style: preserve-3d;
    transition: none;
}

.book__core {
    position: absolute;
    top: 0;
    left: 33.333333%;
    z-index: 1;
    width: 33.333333%;
    height: 100%;
    border: 1px solid var(--color-border);
    border-radius: 1.05rem;
    background:
        linear-gradient(90deg, rgba(255, 255, 255, 0.018), transparent 18%, transparent 82%, rgba(255, 255, 255, 0.012)),
        var(--color-page);
    box-shadow: 0 1.8rem 5rem rgba(0, 0, 0, 0.35);
}

.book__spread {
    position: absolute;
    inset: 0;
    z-index: 4;
    opacity: 0;
    visibility: hidden;
    transform: none;
    pointer-events: none;
    transition: opacity 220ms ease, visibility 0s linear 220ms;
}

.book.is-content-revealing .book__spread,
.book.is-open-complete .book__spread {
    opacity: 1;
    visibility: visible;
    pointer-events: auto;
    transition-delay: 0s;
}

.book-view {
    position: absolute;
    inset: 0;
    display: grid;
    grid-template-columns: repeat(3, minmax(0, 1fr));
    grid-template-rows: minmax(0, 1fr);
    opacity: 1;
    transform: none;
    transition: none;
}

.book-view[hidden] {
    display: none;
}

.book-view > .book__page {
    min-width: 0;
    min-height: 0;
    height: 100%;
    border-radius: 0;
}

.book-view > .book__page:first-child {
    border-radius: 1.1rem 0 0 1.1rem;
    box-shadow:
        inset -1.7rem 0 2.2rem rgba(0, 0, 0, 0.19),
        -1.8rem 1.8rem 4.5rem rgba(0, 0, 0, 0.32);
}

.book-view > .book__page:nth-child(2) {
    box-shadow:
        inset 1.2rem 0 1.8rem rgba(0, 0, 0, 0.12),
        inset -1.2rem 0 1.8rem rgba(0, 0, 0, 0.12),
        0 1.8rem 4.5rem rgba(0, 0, 0, 0.24);
}

.book-view > .book__page:last-child {
    border-radius: 0 1.1rem 1.1rem 0;
    box-shadow:
        inset 1.7rem 0 2.2rem rgba(0, 0, 0, 0.19),
        1.8rem 1.8rem 4.5rem rgba(0, 0, 0, 0.32);
}

.book-view > .book__page::before,
.book-view > .book__page::after {
    pointer-events: none;
}

.book-view > .book__page:nth-child(2)::before,
.book-view > .book__page:nth-child(2)::after {
    content: "";
    position: absolute;
    top: 0;
    bottom: 0;
    width: 1px;
    background: rgba(255, 255, 255, 0.04);
}

.book-view > .book__page:nth-child(2)::before { left: 0; }
.book-view > .book__page:nth-child(2)::after { right: 0; }

.book__page-inner {
    padding: clamp(1.75rem, 2.7vw, 3rem);
}

.book__page h2 {
    font-size: clamp(2.15rem, 3vw, 3.15rem);
}

/* Interaction after opening. */
.book.is-open .book__spread,
.book.is-open-complete .book__spread,
.book.is-open .book-view.is-active,
.book.is-open-complete .book-view.is-active,
.book.is-open .book__page,
.book.is-open-complete .book__page {
    pointer-events: auto;
}

.book.is-open-complete {
    transform-style: flat;
}

.book.is-open-complete .book__spread {
    z-index: 4;
    transform: none;
}

/* Desktop content transitions. */
@media (min-width: 901px) {
    .book-view .book__page-inner {
        opacity: 1;
        transform: translateX(0);
        transition:
            opacity 150ms ease,
            transform 180ms cubic-bezier(0.22, 0.72, 0.2, 1);
    }

    .book:not(.is-open-complete):not(.is-content-revealing) .book-view.is-active .book__page-inner {
        opacity: 0;
        transform: translateY(0.18rem);
    }

    .book.is-content-revealing .book-view.is-active .book__page-inner,
    .book.is-open-complete .book-view.is-active .book__page-inner {
        opacity: 1;
        transform: translateX(0) translateY(0);
    }

    .book-view.is-content-leaving-forward .book__page-inner {
        opacity: 0;
        transform: translateX(-0.65rem);
        pointer-events: none;
    }

    .book-view.is-content-entering-forward .book__page-inner {
        opacity: 0;
        transform: translateX(0.65rem);
        pointer-events: none;
    }

    .book-view.is-content-leaving-backward .book__page-inner {
        opacity: 0;
        transform: translateX(0.65rem);
        pointer-events: none;
    }

    .book-view.is-content-entering-backward .book__page-inner {
        opacity: 0;
        transform: translateX(-0.65rem);
        pointer-events: none;
    }
}

.book__spread,
.book-view,
.book__page {
    min-height: 0;
}

.book-view {
    grid-template-rows: minmax(0, 1fr);
}

/* Folding wings. */
.book__wing {
    position: absolute;
    top: 0;
    width: 33.333333%;
    height: 100%;
    transform-style: preserve-3d;
    transition: transform 640ms cubic-bezier(0.22, 0.72, 0.2, 1);
    will-change: transform;
}

.book__wing--left {
    left: 0;
    z-index: 6;
    transform: rotateY(180deg);
    transform-origin: right center;
}

.book__wing--right {
    right: 0;
    z-index: 7;
    transform: rotateY(-180deg);
    transform-origin: left center;
}

.book.is-opening-right .book__wing--right,
.book.is-right-open .book__wing--right,
.book.is-opening-left .book__wing--right,
.book.is-content-revealing .book__wing--right,
.book.is-open-complete .book__wing--right {
    transform: rotateY(0deg);
}

.book.is-opening-left .book__wing--left,
.book.is-content-revealing .book__wing--left,
.book.is-open-complete .book__wing--left {
    transform: rotateY(0deg);
}

.book__wing-face {
    position: absolute;
    inset: 0;
    overflow: hidden;
    border: 1px solid var(--color-border);
    backface-visibility: hidden;
    -webkit-backface-visibility: hidden;
}

.book__wing-face--inner {
    background:
        repeating-linear-gradient(0deg, rgba(255, 255, 255, 0.008) 0, rgba(255, 255, 255, 0.008) 1px, transparent 1px, transparent 4px),
        linear-gradient(120deg, rgba(79, 140, 138, 0.025), transparent 45%),
        var(--color-page);
}

.book__wing--left .book__wing-face--inner {
    border-radius: 1.1rem 0 0 1.1rem;
    box-shadow: inset -1.5rem 0 2rem rgba(0, 0, 0, 0.18);
}

.book__wing--right .book__wing-face--inner {
    border-radius: 0 1.1rem 1.1rem 0;
    box-shadow: inset 1.5rem 0 2rem rgba(0, 0, 0, 0.18);
}

.book__wing-face--outer {
    transform: rotateY(180deg);
    background:
        repeating-linear-gradient(0deg, rgba(255, 255, 255, 0.012) 0, rgba(255, 255, 255, 0.012) 1px, transparent 1px, transparent 4px),
        repeating-linear-gradient(90deg, rgba(255, 255, 255, 0.009) 0, rgba(255, 255, 255, 0.009) 1px, transparent 1px, transparent 5px),
        linear-gradient(145deg, rgba(255, 255, 255, 0.025), transparent 34%),
        var(--color-cover);
}

.book__wing--right .book__wing-face--outer {
    border-radius: 1.25rem;
    box-shadow:
        inset 1rem 0 1.5rem rgba(0, 0, 0, 0.25),
        1.8rem 2rem 5.5rem rgba(0, 0, 0, 0.44);
}

.book__wing--left .book__wing-face--outer {
    border-radius: 1.1rem;
    background: #15191c;
    box-shadow: inset -1.2rem 0 1.8rem rgba(0, 0, 0, 0.24);
}

.book.is-open-complete .book__wing,
.book.is-open-complete .book__core {
    display: none;
}

.book__wing--right .book-cover__content {
    transform: rotateY(0deg);
}

.book-cover__logo {
    display: flex;
    justify-content: center;
    align-items: center;
    margin: 2.5rem 0 1.5rem;
}

.book-cover__logo img {
    display: block;
    width: 100px;
    height: 100px;
    object-fit: contain;
    filter: brightness(0) invert(1);
    opacity: 0.16;
    mix-blend-mode: screen;
}

/* Three-column home refinements. */
.book-view[data-view="home"] .about-content {
    margin-top: 1.45rem;
}

.book-view[data-view="home"] .about-content__lead {
    font-size: 0.98rem;
}

.book-view[data-view="home"] .about-content__text {
    font-size: 0.84rem;
    line-height: 1.62;
}

.book-view[data-view="home"] .about-profile {
    grid-template-columns: 6.3rem minmax(0, 1fr);
    gap: 0.8rem;
    margin-top: 0.35rem;
    padding-top: 1rem;
}

.book-view[data-view="home"] .about-profile__portrait {
    min-height: 7.8rem;
}

.book-view[data-view="home"] .about-profile__fact {
    grid-template-columns: 5rem minmax(0, 1fr);
    gap: 0.55rem;
    padding: 0.58rem 0.68rem;
}

.book-view[data-view="home"] .about-profile__fact dt {
    font-size: 0.58rem;
}

.book-view[data-view="home"] .about-profile__fact dd {
    font-size: 0.74rem;
}

.book-view[data-view="home"] .portfolio-content {
    gap: 0.72rem;
    margin-top: 1.15rem;
}

.book-view[data-view="home"] .portfolio-content__intro {
    font-size: 0.8rem;
}

.book-view[data-view="home"] .portfolio-projects {
    gap: 0.62rem;
}

.book-view[data-view="home"] .portfolio-card,
.book-view[data-view="home"] .portfolio-card--featured {
    gap: 0.5rem;
    padding: 0.72rem 0.78rem;
}

.book-view[data-view="home"] .portfolio-card__header {
    grid-template-columns: 1.5rem minmax(0, 1fr);
    gap: 0.5rem;
}

.book-view[data-view="home"] .portfolio-card h3 {
    font-size: 1rem;
}

.book-view[data-view="home"] .portfolio-card__description,
.book-view[data-view="home"] .portfolio-card__footer {
    padding-left: 2rem;
}

.book-view[data-view="home"] .portfolio-card__description {
    font-size: 0.7rem;
    line-height: 1.45;
}

.book-view[data-view="home"] .portfolio-card__tag {
    display: inline-flex;
    font-size: 0.53rem;
}

.book-view[data-view="home"] .portfolio-card__footer {
    gap: 0.45rem;
    flex-wrap: wrap;
}

.book-view[data-view="home"] .contact-content {
    gap: 0.78rem;
    margin-top: 1.15rem;
}

.book-view[data-view="home"] .contact-content__intro {
    font-size: 0.8rem;
}

.book-view[data-view="home"] .contact-form {
    gap: 0.62rem;
}

.book-view[data-view="home"] .contact-form__row {
    grid-template-columns: 1fr;
    gap: 0.62rem;
}

.book-view[data-view="home"] .contact-form__input {
    min-height: 2.65rem;
    padding: 0.58rem 0.72rem;
}

.book-view[data-view="home"] .contact-form__textarea {
    min-height: 5.5rem;
}

.book-view[data-view="home"] .contact-captcha {
    grid-template-columns: minmax(8.5rem, 1fr) auto;
}

.book-view[data-view="home"] .contact-captcha__input {
    grid-column: 1 / -1;
}

.book-view[data-view="home"] .contact-form__actions {
    align-items: flex-start;
    flex-direction: column;
    gap: 0.5rem;
}

.book-view[data-view="home"] .contact-form__note {
    max-width: none;
    text-align: left;
}

.book-view--legal .book__page {
    overflow-y: auto;
    scrollbar-width: thin;
    scrollbar-color: rgba(79, 140, 138, 0.3) transparent;
}

.book-view--legal .book__page-inner {
    height: auto;
    min-height: 100%;
}

.book-view.is-content-leaving-forward .book__page-inner,
.book-view.is-content-leaving-backward .book__page-inner,
.book-view.is-content-entering-forward .book__page-inner,
.book-view.is-content-entering-backward .book__page-inner {
    opacity: 0;
}

.book-view .book__page-inner {
    transition: opacity 150ms ease;
}

/* Compact desktop / tablet landscape. */
@media (max-width: 1180px) and (min-width: 901px) {
    .book-scene {
        --page-width: min(31vw, 23rem);
        --book-height: min(76vh, 43rem);
    }

    .book__page-inner {
        padding: 1.55rem 1.35rem;
    }

    .book__page h2 {
        font-size: clamp(1.9rem, 3.5vw, 2.55rem);
    }

    .book-view[data-view="home"] .about-profile {
        grid-template-columns: 1fr;
    }

    .book-view[data-view="home"] .about-profile__portrait {
        width: 6.5rem;
        min-height: 6.5rem;
    }

    .book-view[data-view="home"] .portfolio-card__tag {
        display: none;
    }
}

/* Mobile: one closed cover, then a normal vertical document. */
@media (max-width: 900px) {
    .site-shell {
        grid-template-rows: auto auto;
        min-height: 100svh;
        padding: 1rem clamp(0.75rem, 3vw, 1.25rem) 1.25rem;
    }

    .site-shell:not(.is-book-open) {
        position: fixed;
        inset: 0;
        z-index: 1;
        grid-template-rows: minmax(0, 1fr);
        width: 100%;
        height: 100svh;
        min-height: 0;
        overflow: hidden;
        align-content: stretch;
        place-items: stretch center;
    }

    .site-shell:not(.is-book-open) .site-footer {
        display: none;
    }

    .site-shell:not(.is-book-open) .site-stage,
    .site-shell:not(.is-book-open) .book-experience {
        display: grid;
        place-items: center;
        width: 100%;
        min-height: 0;
    }

    .site-shell:not(.is-book-open) .book-scene {
        width: min(91vw, 24rem);
        height: min(66svh, 34rem);
        perspective: 1800px;
        perspective-origin: center;
    }

    .site-shell:not(.is-book-open) .book {
        width: 100%;
        height: 100%;
    }

    .site-shell:not(.is-book-open) .book__spread {
        display: none;
    }

    .site-shell:not(.is-book-open) .book__core,
    .site-shell:not(.is-book-open) .book__wing--left {
        display: none;
    }

    .site-shell:not(.is-book-open) .book__wing--right {
        inset: 0;
        width: 100%;
        transform: none;
        transform-origin: left center;
    }

    .site-shell:not(.is-book-open) .book__wing--right .book__wing-face--outer {
        transform: none;
        backface-visibility: visible;
    }

    .site-shell:not(.is-book-open) .book__wing--right .book__wing-face--inner {
        display: none;
    }

    .site-shell:not(.is-book-open) .book.is-opening-right .book__wing--right {
        opacity: 0;
        transform: scale(0.97);
        transition: opacity 380ms ease, transform 380ms ease;
    }

    .site-shell.is-book-open {
        position: static;
        grid-template-rows: auto auto;
        align-content: start;
        place-items: stretch center;
        width: 100%;
        height: auto;
        min-height: 100svh;
        overflow: visible;
    }

    .site-shell.is-book-open .book-experience {
        display: block;
    }

    .site-shell.is-book-open .book-scene {
        width: 100%;
        height: auto;
        perspective: none;
    }

    .site-shell.is-book-open .book,
    .site-shell.is-book-open .book.is-open,
    .site-shell.is-book-open .book.is-open-complete {
        position: relative;
        width: 100%;
        height: auto;
        transform: none;
        transform-style: flat;
        transition: none;
    }

    .site-shell.is-book-open .book__spread {
        display: block;
        position: relative;
        inset: auto;
        width: 100%;
        height: auto;
        opacity: 1;
        visibility: visible;
        transform: none;
        pointer-events: auto;
        transition: none;
    }

    .site-shell.is-book-open .book-view {
        position: relative;
        inset: auto;
        grid-template-columns: minmax(0, 1fr);
        grid-template-rows: none;
        gap: 0.8rem;
        width: 100%;
        height: auto;
        opacity: 1;
        transform: none;
        transition: none;
    }

    .site-shell.is-book-open .book-view[hidden] {
        display: none;
    }

    .site-shell.is-book-open .book-view > .book__page,
    .site-shell.is-book-open .book-view > .book__page:first-child,
    .site-shell.is-book-open .book-view > .book__page:nth-child(2),
    .site-shell.is-book-open .book-view > .book__page:last-child {
        width: 100%;
        height: auto;
        min-height: 0;
        overflow: visible;
        border-radius: 1rem;
        box-shadow: 0 1.25rem 3.5rem rgba(0, 0, 0, 0.28);
    }

    .site-shell.is-book-open .book__page--left::after,
    .site-shell.is-book-open .book__page--right::before {
        display: none;
    }

    .site-shell.is-book-open .book__page-inner {
        height: auto;
        min-height: 0;
        padding: clamp(1.4rem, 5vw, 2.2rem);
    }

    .site-shell.is-book-open .book__page h2 {
        font-size: clamp(2.25rem, 10vw, 3.2rem);
    }

    .site-shell.is-book-open .book__wing,
    .site-shell.is-book-open .book__core {
        display: none;
    }

    .book-view[data-view="home"] .about-profile {
        grid-template-columns: minmax(6.75rem, 8.5rem) minmax(0, 1fr);
    }

    .book-view[data-view="home"] .portfolio-card__tag {
        display: inline-flex;
    }

    .book-view[data-view="home"] .contact-form__row {
        grid-template-columns: repeat(2, minmax(0, 1fr));
    }

    .book-view[data-view="home"] .contact-captcha {
        grid-template-columns: 10.5rem auto minmax(0, 1fr);
    }

    .book-view[data-view="home"] .contact-captcha__input {
        grid-column: auto;
    }

    .book-view[data-view="home"] .contact-form__actions {
        align-items: center;
        flex-direction: row;
    }

    .book-view[data-view="home"] .contact-form__note {
        max-width: 14rem;
        text-align: right;
    }
}

@media (max-width: 620px) {
    .site-shell {
        padding-inline: 0.65rem;
    }

    .site-shell:not(.is-book-open) .book-scene {
        width: min(91vw, 24rem);
        height: min(66svh, 34rem);
    }

    .site-shell.is-book-open .book-view {
        gap: 0.75rem;
    }

    .site-shell.is-book-open .book__page-inner {
        padding: 1.35rem 1.2rem 1.5rem;
    }

    .book-view[data-view="home"] .about-profile {
        grid-template-columns: 1fr;
    }

    .book-view[data-view="home"] .contact-form__row {
        grid-template-columns: 1fr;
    }

    .book-view[data-view="home"] .contact-captcha {
        grid-template-columns: minmax(0, 1fr) auto;
    }

    .book-view[data-view="home"] .contact-captcha__input {
        grid-column: 1 / -1;
    }

    .book-view[data-view="home"] .contact-form__actions {
        align-items: flex-start;
        flex-direction: column;
    }

    .book-view[data-view="home"] .contact-form__note {
        max-width: none;
        text-align: left;
    }
}

/* Desktop readability refinements formerly split into trifold-readability.css. */
@media (min-width: 1181px) {
    .site-stage {
        width: min(100%, 1720px);
    }

    .book-scene {
        transition: width 360ms cubic-bezier(0.22, 0.72, 0.2, 1);
    }

    .book__page-inner {
        padding: clamp(2rem, 2.5vw, 3.35rem);
    }

    .book__page h2 {
        font-size: clamp(2.3rem, 3vw, 3.35rem);
    }

    .book-view[data-view="home"] .about-content__lead {
        font-size: 1.06rem;
        line-height: 1.68;
    }

    .book-view[data-view="home"] .about-content__text {
        font-size: 0.92rem;
        line-height: 1.68;
    }

    .book-view[data-view="home"] .about-profile__fact dt {
        font-size: 0.61rem;
    }

    .book-view[data-view="home"] .about-profile__fact dd {
        font-size: 0.8rem;
    }

    .book-view[data-view="home"] .portfolio-content__intro {
        font-size: 0.88rem;
        line-height: 1.62;
    }

    .book-view[data-view="home"] .portfolio-card h3 {
        font-size: 1.08rem;
    }

    .book-view[data-view="home"] .portfolio-card__description {
        font-size: 0.78rem;
        line-height: 1.52;
    }

    .book-view[data-view="home"] .portfolio-card__tag {
        font-size: 0.57rem;
    }

    .book-view[data-view="home"] .contact-content__intro {
        font-size: 0.88rem;
        line-height: 1.62;
    }

    .book-view[data-view="home"] .contact-form__label {
        font-size: 0.66rem;
    }

    .book-view[data-view="home"] .contact-form__input,
    .book-view[data-view="home"] .contact-form__textarea {
        font-size: 0.9rem;
    }

    .book-view[data-view="home"] .contact-form__note {
        font-size: 0.72rem;
    }
}

/* Compact CAPTCHA refinements formerly split into trifold-details.css. */
.book-view[data-view="home"] .contact-captcha {
    grid-template-columns: 9.75rem 3rem minmax(7.5rem, 1fr);
    gap: 0.55rem;
    align-items: center;
}

.book-view[data-view="home"] .contact-captcha__image {
    width: 9.75rem;
    height: 3rem;
    border: 1px solid rgba(79, 140, 138, 0.14);
    border-radius: 0.68rem;
}

.book-view[data-view="home"] .contact-captcha__refresh {
    width: 3rem;
    min-width: 3rem;
    min-height: 3rem;
    height: 3rem;
    padding: 0;
    border-radius: 0.68rem;
    font-size: 0;
}

.book-view[data-view="home"] .contact-captcha__refresh::before {
    content: "↻";
    color: currentColor;
    font-size: 1.15rem;
    line-height: 1;
}

.book-view[data-view="home"] .contact-captcha__input {
    grid-column: auto;
    height: 3rem;
    min-height: 3rem;
    padding-inline: 0.78rem;
}

@media (max-width: 1180px) and (min-width: 901px) {
    .book-view[data-view="home"] .contact-captcha {
        grid-template-columns: 8.25rem 2.75rem minmax(0, 1fr);
    }

    .book-view[data-view="home"] .contact-captcha__image {
        width: 8.25rem;
    }

    .book-view[data-view="home"] .contact-captcha__refresh {
        width: 2.75rem;
        min-width: 2.75rem;
    }
}

@media (max-width: 900px) {
    .book-view[data-view="home"] .contact-captcha {
        grid-template-columns: 10rem 3rem minmax(0, 1fr);
    }

    .book-view[data-view="home"] .contact-captcha__image {
        width: 10rem;
    }
}

@media (max-width: 620px) {
    .book-view[data-view="home"] .contact-captcha {
        grid-template-columns: minmax(0, 1fr) 3rem;
    }

    .book-view[data-view="home"] .contact-captcha__image {
        width: 100%;
    }

    .book-view[data-view="home"] .contact-captcha__input {
        grid-column: 1 / -1;
    }
}

/* Inner-cover branding during opening and closing. */
@media (min-width: 901px) {
    .book.is-opening-left .book__wing--right .book__wing-face--outer::after,
    .book.is-left-open .book__wing--right .book__wing-face--outer::after,
    .book.is-closing-right .book__wing--right .book__wing-face--outer::after {
        content: "";
        position: absolute;
        inset: 0;
        z-index: 1;
        background-image: url('../images/Logo.png');
        background-position: center;
        background-repeat: no-repeat;
        background-size: clamp(9rem, 42%, 13rem) auto;
        filter: brightness(0) invert(1);
        opacity: 0.16;
        mix-blend-mode: screen;
        pointer-events: none;
    }
}

/* Name and E-Mail stay in one row from tablet upwards. */
@media (min-width: 621px) {
    .book-view[data-view="home"] .contact-form__row {
        grid-template-columns: repeat(2, minmax(0, 1fr));
    }
}

/* Book close control formerly split into book-close.css. */
.book-close-button {
    position: absolute;
    top: -1px;
    right: 1.2rem;
    z-index: 20;
    display: inline-flex;
    align-items: flex-start;
    justify-content: center;
    width: 2.7rem;
    height: 3.35rem;
    padding: 0.62rem 0 0;
    border: 1px solid rgba(103, 170, 167, 0.22);
    border-top: 0;
    background:
        linear-gradient(180deg, rgba(103, 170, 167, 0.08), transparent 65%),
        #171c1f;
    color: rgba(236, 233, 227, 0.86);
    box-shadow:
        0 0.55rem 1.25rem rgba(0, 0, 0, 0.18),
        inset 0 0 0 1px rgba(255, 255, 255, 0.018);
    clip-path: polygon(0 0, 100% 0, 100% 100%, 50% 79%, 0 100%);
    cursor: pointer;
    opacity: 0;
    visibility: hidden;
    pointer-events: none;
    transform: translateY(-0.35rem);
    transition:
        opacity 160ms ease,
        visibility 0s linear 160ms,
        transform 160ms ease,
        color var(--transition-fast),
        background var(--transition-fast),
        border-color var(--transition-fast);
}

.site-shell.is-book-open .book-close-button {
    opacity: 1;
    visibility: visible;
    pointer-events: auto;
    transform: translateY(0);
    transition-delay: 0s;
}

.book-close-button > span[aria-hidden="true"] {
    display: block;
    font-family: var(--font-sans);
    font-size: 1.45rem;
    font-weight: 500;
    line-height: 1;
}

.book-close-button:hover {
    border-color: rgba(103, 170, 167, 0.46);
    background:
        linear-gradient(180deg, rgba(103, 170, 167, 0.17), transparent 68%),
        #1b2225;
    color: var(--color-accent-hover);
}

.book-close-button:focus-visible {
    outline: 2px solid var(--color-accent);
    outline-offset: 0.22rem;
}

.book-close-button:active {
    transform: translateY(1px);
}

@media (max-width: 900px) {
    .book-close-button {
        top: 0;
        right: 0.85rem;
        width: 2.5rem;
        height: 3.05rem;
        padding-top: 0.55rem;
    }

    .book-close-button > span[aria-hidden="true"] {
        font-size: 1.3rem;
    }
}

@media (prefers-reduced-motion: reduce) {
    .book-scene,
    .book__wing,
    .book__spread,
    .book-view .book__page-inner,
    .book-close-button {
        transition: none !important;
    }
}