book.css

:root {
    /* colors */
    --book-shadow-color: #1d1d1d;
    --book-page-color: #bca994;
    --book-page-color-shade: #92806b;
    --book-page-color-side: #81715e;
    --book-page-color-highlight: #ded1bf;
    --book-page-shade-opacity: 0.7;
    --book-page-slot-color: #9d9d9d;
    --book-page-slot-color-icon-neutral: #949494;

    /* dimensions */
    --book-page-shade-size: 95%;
    --book-page-skew: 30;
    --book-shadow-radius: 12px;
    --book-hide-time: 0.5s;
    --book-button-padding: 16px;
    --page-button-padding: 10px;
    --page-button-page-shift: 0.75;
    --page-button-color-enabled: #75a757;
    --page-button-color-disabled: gray;
    --page-button-color-unfulfilled: #a43333;
    --page-button-shadow-radius: 4px;
}

#book {
    pointer-events: auto;
    position: absolute;
    background-color: var(--card-color-background);
    display: flex;
    align-items: center;
    transition: var(--book-hide-time) ease;
    transition-property: top;
    box-shadow: 0 0 var(--book-shadow-radius) var(--book-shadow-color);
    user-select: none;
    border-radius: var(--card-border-radius);
}

#book.hidden {
    top: -100% !important;
}

#book.invisible {
    visibility: hidden;
}

#book #spine {
    width: 0;
    margin-left: auto;
    margin-right: auto;
    position: relative;
}

#book #spine .page {
    position: absolute;
    display: none;
    justify-content: space-evenly;
    align-items: center;
    flex-wrap: wrap;
    overflow: hidden;
}

#book #spine .page .overlay {
    position: absolute;
    pointer-events: none;
    width: 100%;
    height: 100%;
    opacity: 0;
}

#book #spine .page .overlay.left {
    background-color: var(--color-white);
}

#book #spine .page .overlay.right {
    background-color: black;
}

#book #spine .page.visible {
    display: flex;
}

#book #spine .page.left {
    right: 0;
    background: linear-gradient(
        to right,
        var(--book-page-color) var(--book-page-shade-size),
        var(--book-page-color-highlight));
    transform-origin: right;
    border-top-left-radius: var(--card-border-radius);
    border-bottom-left-radius: var(--card-border-radius);
}

#book #spine .page.right {
    left: 0;
    background: linear-gradient(
        to left,
        var(--book-page-color) var(--book-page-shade-size),
        var(--book-page-color-shade));
    transform-origin: left;
    border-top-right-radius: var(--card-border-radius);
    border-bottom-right-radius: var(--card-border-radius);
}

#book #spine .page .slot {
    position: relative;
    background-color: var(--book-page-slot-color);
    border-radius: var(--card-border-radius);
    overflow: hidden;
}

#book #spine .page .slot svg {
    position: absolute;
    width: 100%;
    height: 100%;
}

#book #spine .page .slot .card {
    margin: 0;
    transform-origin: left top;
    box-shadow: none;
}

#button-book {
    position: absolute;
    right: var(--book-button-padding);
    top: var(--book-button-padding);
}

#button-book svg {
    filter: drop-shadow(0 0 var(--page-button-shadow-radius) var(--book-shadow-color));
}

#button-book:active path.page {
    fill: var(--color-white);
}

#button-book path.side {
    fill: var(--book-page-color-side);
}

.button-page {
    position: absolute;
}

.button-page div {
    position: absolute;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    display: flex;
    align-items: center;
}

.button-page div p {
    margin: 0;
    padding-left: var(--page-button-padding);
}

.button-page svg {
    filter: drop-shadow(0 0 var(--page-button-shadow-radius) var(--book-shadow-color));
}

.button-page path {
    fill: var(--page-button-color-enabled);
}

.button-page:active path {
    fill: var(--color-white);
}

.button-page.locked path {
    fill: var(--page-button-color-unfulfilled);
    pointer-events: none;
}

.button-page.disabled path {
    fill: var(--page-button-color-disabled);
    pointer-events: none;
}

.button-page.left {
    left: calc(var(--button-width) * var(--page-button-page-shift) * -1);
}

.button-page.right {
    right: calc(var(--button-width) * var(--page-button-page-shift) * -1);
}