.be-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 2rem 1.5rem 4rem;
}

.be-header {
    text-align: center;
    margin-bottom: 1.5rem;
}

.be-header h1 {
    font-size: 2.2rem;
    margin-bottom: 0.5rem;
    color: var(--text-primary);
}

.be-header p {
    color: var(--text-secondary);
    max-width: 640px;
    margin: 0 auto;
}

.be-breadcrumbs {
    font-size: 0.85rem;
    color: var(--text-secondary);
    margin-bottom: 0.75rem;
    text-align: left;
}

.be-breadcrumbs a {
    color: var(--accent-blue);
    text-decoration: none;
}

.be-breadcrumbs a:hover {
    text-decoration: underline;
}

.be-breadcrumbs span[aria-hidden] {
    margin: 0 0.4rem;
    color: var(--text-muted);
}

/* Search + actions */

.be-search {
    display: flex;
    gap: 0.5rem;
    max-width: 480px;
    margin: 0 auto 1rem;
}

.be-search input {
    flex: 1;
    padding: 0.6rem 0.9rem;
    border-radius: 8px;
    border: 1px solid rgba(0, 212, 255, 0.2);
    background: var(--tertiary-dark);
    color: var(--text-primary);
}

.be-search button {
    padding: 0.6rem 1.1rem;
    border-radius: 8px;
    border: 1px solid var(--accent-blue);
    background: transparent;
    color: var(--accent-blue);
    cursor: pointer;
}

.be-search button:hover {
    background: rgba(0, 212, 255, 0.12);
}

.be-actions {
    text-align: center;
    margin-bottom: 2rem;
}

.be-surprise {
    display: inline-block;
    padding: 0.5rem 1.1rem;
    border-radius: 20px;
    border: 1px solid var(--accent-purple);
    color: var(--text-primary);
    text-decoration: none;
    transition: background 0.2s ease;
}

.be-surprise:hover {
    background: rgba(108, 92, 231, 0.15);
}

/* Topic shelves */

.be-shelves {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
    gap: 1rem;
}

.be-shelf-card {
    display: flex;
    flex-direction: column;
    gap: 0.4rem;
    padding: 1.25rem 1.4rem;
    background: var(--tertiary-dark);
    border: 1px solid rgba(0, 212, 255, 0.15);
    border-radius: 12px;
    text-decoration: none;
    transition: border-color 0.2s ease, transform 0.2s ease;
}

.be-shelf-card:hover {
    border-color: var(--accent-blue);
    transform: translateY(-2px);
}

.be-shelf-card h2 {
    font-size: 1.1rem;
    color: var(--text-primary);
    margin: 0;
}

.be-shelf-count {
    font-size: 0.8rem;
    color: var(--text-secondary);
}

.be-empty-state {
    text-align: center;
    padding: 3rem 1rem;
    color: var(--text-secondary);
}

/* Browse layout */

.be-browse-layout {
    display: grid;
    grid-template-columns: 240px 1fr;
    gap: 2rem;
    align-items: start;
}

.be-filters {
    background: var(--secondary-dark);
    border: 1px solid rgba(0, 212, 255, 0.12);
    border-radius: 12px;
    padding: 1.25rem;
    position: sticky;
    top: 1rem;
}

.be-filters h2 {
    font-size: 1rem;
    margin: 0 0 1rem;
}

.be-filter-group {
    margin-bottom: 1.25rem;
}

.be-filter-group h3 {
    font-size: 0.8rem;
    text-transform: uppercase;
    letter-spacing: 0.04em;
    color: var(--text-secondary);
    margin: 0 0 0.5rem;
}

.be-filter-group select {
    width: 100%;
    padding: 0.4rem 0.5rem;
    border-radius: 6px;
    border: 1px solid rgba(0, 212, 255, 0.2);
    background: var(--tertiary-dark);
    color: var(--text-primary);
}

.be-chips {
    display: flex;
    flex-wrap: wrap;
    gap: 0.4rem;
}

.be-chip {
    padding: 0.3rem 0.7rem;
    border-radius: 14px;
    border: 1px solid rgba(0, 212, 255, 0.2);
    background: var(--tertiary-dark);
    color: var(--text-secondary);
    font-size: 0.78rem;
    cursor: pointer;
    text-decoration: none;
}

.be-chip:hover {
    border-color: var(--accent-blue);
    color: var(--text-primary);
}

.be-chip.active {
    background: rgba(0, 212, 255, 0.18);
    border-color: var(--accent-blue);
    color: var(--text-primary);
}

.be-chip-static {
    display: inline-block;
}

.be-checkbox {
    display: flex;
    align-items: center;
    gap: 0.4rem;
    font-size: 0.8rem;
    color: var(--text-secondary);
    margin-top: 0.6rem;
}

/* Results grid */

.be-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(160px, 1fr));
    gap: 1.25rem;
}

.be-card {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
    text-decoration: none;
    color: var(--text-primary);
}

.be-card-cover {
    aspect-ratio: 2 / 3;
    border-radius: 8px;
    overflow: hidden;
    background: var(--tertiary-dark);
    display: flex;
    align-items: center;
    justify-content: center;
}

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

.be-card-cover-placeholder {
    font-size: 2.5rem;
    font-family: 'Syne', sans-serif;
    color: var(--text-muted);
}

.be-card h3 {
    font-size: 0.9rem;
    margin: 0;
    line-height: 1.3;
}

.be-card-author {
    font-size: 0.78rem;
    color: var(--text-secondary);
    margin: 0;
}

.be-card-meta {
    font-size: 0.75rem;
    color: var(--text-muted);
    margin: 0;
    display: flex;
    gap: 0.5rem;
}

.be-card-rating {
    color: var(--accent-blue);
}

.be-load-more {
    display: block;
    margin: 2rem auto 0;
    padding: 0.6rem 1.5rem;
    border-radius: 20px;
    border: 1px solid var(--accent-blue);
    background: transparent;
    color: var(--accent-blue);
    cursor: pointer;
}

.be-load-more:hover {
    background: rgba(0, 212, 255, 0.12);
}

/* Book detail page */

.be-book-layout {
    display: grid;
    grid-template-columns: 240px 1fr;
    gap: 2rem;
    margin-bottom: 2rem;
}

.be-book-cover img {
    width: 100%;
    border-radius: 10px;
}

.be-book-cover-placeholder {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 240px;
    height: 360px;
    border-radius: 10px;
    background: var(--tertiary-dark);
    font-size: 4rem;
}

.be-book-info h1 {
    margin: 0 0 0.25rem;
    font-size: 1.8rem;
}

.be-book-subtitle {
    color: var(--text-secondary);
    margin: 0 0 0.5rem;
}

.be-book-author {
    color: var(--text-secondary);
    margin: 0 0 0.75rem;
}

.be-book-meta {
    display: flex;
    gap: 1rem;
    flex-wrap: wrap;
    font-size: 0.85rem;
    color: var(--text-muted);
    margin: 0 0 1rem;
}

.be-book-chips {
    display: flex;
    flex-wrap: wrap;
    gap: 0.4rem;
    margin-bottom: 1rem;
}

.be-chip-genre {
    background: rgba(108, 92, 231, 0.15);
    border-color: var(--accent-purple);
    font-weight: 600;
}

.be-chip-genre:hover {
    background: rgba(108, 92, 231, 0.28);
}

.be-book-blurb {
    color: var(--text-secondary);
    line-height: 1.6;
    margin-bottom: 1.25rem;
}

.be-book-links {
    display: flex;
    flex-wrap: wrap;
    gap: 0.6rem;
}

.be-link-btn {
    padding: 0.55rem 1.1rem;
    border-radius: 8px;
    border: 1px solid rgba(0, 212, 255, 0.25);
    color: var(--text-primary);
    text-decoration: none;
    font-size: 0.85rem;
}

.be-link-btn:hover {
    border-color: var(--accent-blue);
    background: rgba(0, 212, 255, 0.1);
}

.be-link-primary {
    background: var(--accent-blue);
    border-color: var(--accent-blue);
    color: var(--primary-dark);
    font-weight: 600;
}

.be-link-primary:hover {
    background: var(--accent-blue);
    opacity: 0.9;
}

.be-reader {
    margin-top: 1.5rem;
}

.be-reader h2 {
    font-size: 1.1rem;
    margin-bottom: 0.75rem;
}

.be-reader iframe {
    width: 100%;
    height: 700px;
    border: 1px solid rgba(0, 212, 255, 0.15);
    border-radius: 10px;
    background: #fff;
}

.be-reader-fallback {
    font-size: 0.8rem;
    color: var(--text-muted);
    margin-top: 0.5rem;
}

@media (max-width: 800px) {
    .be-browse-layout,
    .be-book-layout {
        grid-template-columns: 1fr;
    }

    .be-filters {
        position: static;
    }

    .be-book-cover img,
    .be-book-cover-placeholder {
        width: 180px;
        height: 270px;
        margin: 0 auto;
    }

    .be-reader iframe {
        height: 480px;
    }
}

/* ===========================================================================
   Single-page layout: fixed sidebar (collapsible subject/place/era/person
   tree + filters) and an AJAX result grid that never navigates away.
   =========================================================================== */

.books-layout {
    display: flex;
    min-height: 100vh;
}

.books-sidebar {
    position: fixed;
    left: 0;
    top: 0;
    width: 300px;
    height: 100vh;
    background: var(--secondary-dark);
    border-right: 1px solid rgba(0, 212, 255, 0.12);
    color: var(--text-primary);
    padding: 1.5rem 1.2rem;
    overflow-y: auto;
    z-index: 100;
    box-sizing: border-box;
}

.books-sidebar-header {
    margin-bottom: 1rem;
    padding-bottom: 1rem;
    border-bottom: 1px solid rgba(0, 212, 255, 0.15);
}

.books-sidebar-title {
    font-size: 1.3rem;
    font-weight: 700;
    margin: 0 0 0.3rem 0;
    color: var(--text-primary);
}

.books-sidebar-title-link {
    text-decoration: none;
    display: inline-block;
}
.books-sidebar-title-link:hover .books-sidebar-title {
    opacity: 0.85;
}

.books-sidebar-subtitle {
    font-size: 0.78rem;
    color: var(--text-secondary);
    margin: 0;
}

.books-sidebar .be-search,
.books-sidebar .be-surprise {
    max-width: none;
    margin: 0 0 0.9rem;
}

.books-sidebar .be-surprise {
    display: block;
    text-align: center;
}

.books-genre-section {
    margin-bottom: 0.4rem;
    border-top: 1px solid rgba(0, 212, 255, 0.1);
    padding-top: 0.4rem;
}

.genre-section-toggle {
    display: flex;
    align-items: center;
    justify-content: space-between;
    width: 100%;
    background: none;
    border: none;
    color: var(--text-secondary);
    font-size: 0.75rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    padding: 0.4rem 0.1rem;
    cursor: pointer;
}

.genre-section-toggle:hover { color: var(--text-primary); }

.genre-section-toggle::after {
    content: '\25B8';
    transition: transform 0.15s ease;
}

.genre-section-toggle[aria-expanded="true"]::after {
    transform: rotate(90deg);
}

.books-genre-tree {
    display: flex;
    flex-direction: column;
    gap: 0.25rem;
    padding-top: 0.35rem;
    flex-wrap: wrap;
}

.books-genre-tree[hidden] { display: none; }

.genre-group-header {
    display: flex;
    align-items: stretch;
    gap: 0.2rem;
}

.genre-group-load {
    flex: 1;
    min-width: 0;
    text-align: left;
    background: none;
    border: none;
    border-radius: 6px;
    color: var(--text-secondary);
    padding: 0.4rem 0.4rem;
    font-size: 0.82rem;
    cursor: pointer;
}

.genre-group-load:hover {
    background: rgba(0, 212, 255, 0.08);
    color: var(--text-primary);
}

.genre-group-load.active {
    color: var(--accent-blue);
    font-weight: 700;
}

.genre-count {
    font-size: 0.68rem;
    color: var(--text-muted);
    margin-left: 0.3rem;
}

.genre-group-expand {
    flex-shrink: 0;
    background: none;
    border: none;
    border-radius: 6px;
    color: var(--text-muted);
    padding: 0.4rem 0.5rem;
    cursor: pointer;
}

.genre-group-expand:hover { background: rgba(0, 212, 255, 0.08); }

.genre-chevron {
    display: inline-block;
    font-size: 0.7rem;
    transition: transform 0.15s ease;
}

.genre-group-expand[aria-expanded="true"] .genre-chevron {
    transform: rotate(90deg);
}

.genre-group-list {
    display: flex;
    flex-direction: column;
    gap: 0.3rem;
    padding: 0.2rem 0.3rem 0.5rem 1rem;
}

.genre-group-list[hidden] { display: none; }

/* A category's tags wrap horizontally to fill the sidebar width. */
.genre-leaf-list {
    flex-direction: row;
    flex-wrap: wrap;
    gap: 0.3rem;
}

.books-genre-tree .genre-chip {
    display: inline-flex;
    align-self: flex-start;
    margin: 0 0.3rem 0.3rem 0;
    padding: 0.3rem 0.65rem;
    border-radius: 14px;
    border: 1px solid rgba(0, 212, 255, 0.2);
    background: var(--tertiary-dark);
    color: var(--text-secondary);
    font-size: 0.76rem;
    cursor: pointer;
}

.books-genre-tree .genre-chip:hover {
    border-color: var(--accent-blue);
    color: var(--text-primary);
}

.books-genre-tree .genre-chip.active {
    background: rgba(0, 212, 255, 0.18);
    border-color: var(--accent-blue);
    color: var(--text-primary);
    font-weight: 600;
}

.genre-show-more {
    display: inline-flex;
    align-self: flex-start;
    margin: 0 0.3rem 0.3rem 0;
    padding: 0.3rem 0.65rem;
    border-radius: 14px;
    border: 1px dashed rgba(0, 212, 255, 0.3);
    background: none;
    color: var(--accent-blue);
    font-size: 0.76rem;
    cursor: pointer;
}

.genre-show-more:hover {
    background: rgba(0, 212, 255, 0.08);
}

.genre-show-more:disabled {
    opacity: 0.6;
    cursor: default;
}

.books-back-link {
    display: inline-flex;
    align-items: center;
    gap: 0.35rem;
    color: var(--text-muted);
    text-decoration: none;
    font-size: 0.82rem;
    margin-top: 1.5rem;
}
.books-back-link:hover { color: var(--text-primary); }

.books-main {
    margin-left: 300px;
    flex: 1;
    padding: 1.75rem 2rem 4rem;
    min-width: 0;
}

.books-header {
    margin-bottom: 1.2rem;
}

.books-page-title {
    font-size: 1.6rem;
    font-weight: 700;
    color: var(--text-primary);
    margin: 0 0 0.25rem 0;
}

.books-result-count {
    font-size: 0.85rem;
    color: var(--text-secondary);
    margin: 0;
}

.books-empty {
    text-align: center;
    padding: 3rem 1rem;
    color: var(--text-secondary);
}
.books-empty-icon { font-size: 3rem; margin-bottom: 0.5rem; }
.books-empty-text { font-size: 1rem; }

@media (max-width: 900px) {
    .books-sidebar {
        position: relative;
        width: 100%;
        height: auto;
    }
    .books-main {
        margin-left: 0;
    }
    .books-layout {
        flex-direction: column;
    }
}