/* ===== CSS Variables ===== */
:root {
    /* Soft lavender palette */
    --bg-primary: #FAF5FF;
    --bg-secondary: #FFFFFF;
    --bg-tertiary: #F3E8FF;

    /* Neutral accent */
    --accent: #292524;
    --accent-hover: #1C1917;

    /* Text colors */
    --text-primary: #292524;
    --text-secondary: #57534E;
    --text-muted: #A8A29E;

    /* Borders */
    --border-light: #E7E5E4;
    --border-medium: #D6D3D1;

    /* Shadows - warmer tone */
    --shadow-sm: 0 1px 3px rgba(41, 37, 36, 0.06);
    --shadow-md: 0 4px 12px rgba(41, 37, 36, 0.08);
    --shadow-lg: 0 12px 40px rgba(41, 37, 36, 0.15);
    --shadow-xl: 0 25px 60px rgba(41, 37, 36, 0.25);

    /* Transitions */
    --transition-fast: 0.15s ease;
    --transition-medium: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

/* ===== Reset & Base ===== */
*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html {
    font-size: 16px;
    scroll-behavior: smooth;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    background: var(--bg-primary);
    min-height: 100vh;
    color: var(--text-primary);
    line-height: 1.6;
}

/* ===== Header ===== */
.header {
    position: relative;
    text-align: center;
    padding: 3rem 1rem 1.5rem;
    background: transparent;
    border-bottom: none;
}

.header h1 {
    font-size: clamp(2rem, 5vw, 3rem);
    font-weight: 700;
    color: var(--text-primary);
    letter-spacing: -0.02em;
    margin-bottom: 0.25rem;
}

.subtitle {
    font-size: 0.9rem;
    color: var(--text-muted);
    font-weight: 400;
    letter-spacing: 0.02em;
}

/* ===== Bookshelf Container - Recessed Shadow Box Effect ===== */
.bookshelf-container {
    max-width: 1300px;
    margin: 0 auto 2rem;
    margin-left: auto;
    margin-right: auto;
    padding: 1.5rem 2.5rem;
    background: rgba(0, 0, 0, 0.025);
    border-radius: 20px;
    box-shadow:
        inset 0 2px 12px rgba(0, 0, 0, 0.06),
        inset 0 1px 3px rgba(0, 0, 0, 0.08),
        inset 0 -2px 0 rgba(255, 255, 255, 0.7);
    border: 1px solid rgba(0, 0, 0, 0.04);
}

/* ===== Bookshelf - now a simple container ===== */
.bookshelf {
    display: flex;
    flex-direction: column;
    gap: 0;
}

/* ===== Shelf Sections ===== */
.shelf-section {
    margin-bottom: 3rem;
}

.shelf-section:last-child {
    margin-bottom: 0;
}

.shelf-header {
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--text-secondary);
    margin-bottom: 1.5rem;
    padding-bottom: 0.75rem;
    border-bottom: 1px solid var(--border-light);
    letter-spacing: 0.01em;
}

.show-more-btn {
    display: block;
    margin: 2rem auto 0;
    padding: 0.75rem 2rem;
    background: var(--bg-secondary);
    color: var(--text-primary);
    border: 1px solid var(--border-medium);
    border-radius: 8px;
    font-family: inherit;
    font-size: 0.95rem;
    font-weight: 500;
    cursor: pointer;
    transition: background var(--transition-fast), box-shadow var(--transition-fast);
}

.show-more-btn:hover {
    background: var(--bg-tertiary);
    box-shadow: var(--shadow-sm);
}

.show-more-btn:focus-visible {
    outline: 2px solid var(--accent);
    outline-offset: 2px;
}

/* ===== Shelf Row - converted to grid ===== */
.shelf-row {
    position: relative;
    padding: 0;
    min-height: auto;
    background: transparent;
    box-shadow: none;
    border-radius: 0;
}

/* Remove shelf decorations */
.shelf-row::after,
.shelf-row::before {
    display: none;
}

/* ===== Books Container - 6 Column Grid ===== */
.books-container {
    display: grid;
    grid-template-columns: repeat(auto-fit, 160px);
    justify-content: center;
    gap: 2rem;
    row-gap: 5rem;
    padding: 0;
    margin-bottom: 2rem;
    min-height: auto;
}

.shelf-row:last-child .books-container {
    margin-bottom: 0;
}

/* ===== Individual Book ===== */
.book {
    position: relative;
    cursor: pointer;
    transition: transform var(--transition-medium);
    border-radius: 8px;
    background: transparent;
    padding: 0;
}

.book:hover {
    transform: translateY(-12px) scale(1.05) rotate(-1deg);
}

.book:nth-child(even):hover {
    transform: translateY(-12px) scale(1.05) rotate(1deg);
}

.book:focus {
    outline: 2px solid var(--accent);
    outline-offset: 2px;
}

/* Remove spine effect */
.book::before {
    display: none;
}

.book-cover {
    width: 100%;
    height: auto;
    aspect-ratio: 2 / 3;
    object-fit: cover;
    border-radius: 8px;
    box-shadow: var(--shadow-md);
    transition: box-shadow var(--transition-medium);
}

.book:hover .book-cover {
    box-shadow: var(--shadow-xl);
}

/* ===== Overlay & Modal ===== */
.overlay {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0.5);
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 1rem;
    z-index: 1000;
    opacity: 0;
    visibility: hidden;
    transition: opacity var(--transition-medium), visibility var(--transition-medium);
    backdrop-filter: blur(4px);
}

.overlay.active {
    opacity: 1;
    visibility: visible;
}

.modal {
    background: var(--bg-secondary);
    border-radius: 16px;
    max-width: 720px;
    width: 100%;
    max-height: 90vh;
    overflow-y: auto;
    position: relative;
    box-shadow: var(--shadow-lg);
    transform: translateY(16px) scale(0.98);
    transition: transform var(--transition-medium);
}

.overlay.active .modal {
    transform: translateY(0) scale(1);
}

.modal-close {
    position: absolute;
    top: 1rem;
    right: 1rem;
    background: var(--bg-tertiary);
    border: none;
    font-size: 1.5rem;
    color: var(--text-secondary);
    cursor: pointer;
    width: 40px;
    height: 40px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 50%;
    transition: background var(--transition-fast), color var(--transition-fast);
    z-index: 10;
}

.modal-close:hover {
    background: var(--border-light);
    color: var(--text-primary);
}

.modal-content {
    display: grid;
    grid-template-columns: 180px 1fr;
    gap: 2rem;
    padding: 2rem;
}

.modal-cover {
    flex-shrink: 0;
}

.modal-cover img {
    width: 100%;
    height: auto;
    aspect-ratio: 2 / 3;
    object-fit: cover;
    border-radius: 8px;
    box-shadow: var(--shadow-md);
}

.modal-details {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.modal-title {
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--text-primary);
    line-height: 1.3;
    padding-right: 3rem;
    letter-spacing: -0.01em;
}

.modal-author {
    font-size: 1rem;
    color: var(--text-secondary);
}

.modal-meta {
    display: flex;
    flex-wrap: wrap;
    gap: 1.5rem;
    padding: 1rem 0;
    border-top: 1px solid var(--border-light);
    border-bottom: 1px solid var(--border-light);
}

.meta-item {
    display: flex;
    flex-direction: column;
    gap: 0.25rem;
}

.meta-label {
    font-size: 0.7rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: var(--text-muted);
    font-weight: 500;
}

.meta-value {
    font-size: 0.95rem;
    color: var(--text-primary);
    font-weight: 500;
}

.modal-notes {
    flex-grow: 1;
}

.modal-notes h3 {
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 0.5rem;
    text-transform: uppercase;
    letter-spacing: 0.03em;
}

.modal-notes p {
    color: var(--text-muted);
    line-height: 1.7;
    white-space: pre-wrap;
    font-size: 0.9rem;
}

.modal-button {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    padding: 0.75rem 1.5rem;
    background: var(--accent);
    color: white;
    text-decoration: none;
    font-family: inherit;
    font-size: 0.95rem;
    font-weight: 500;
    border-radius: 8px;
    transition: background var(--transition-fast), transform var(--transition-fast);
    margin-top: auto;
    align-self: flex-start;
}

.modal-button:hover {
    background: var(--accent-hover);
    transform: translateY(-1px);
}

/* ===== Footer ===== */
.footer {
    text-align: center;
    padding: 2rem 1rem 3rem;
    color: var(--text-muted);
    font-size: 0.875rem;
    background: transparent;
}

/* ===== Loading State ===== */
.loading {
    display: flex;
    align-items: center;
    justify-content: center;
    min-height: 300px;
    color: var(--text-secondary);
    font-size: 1rem;
}

.loading::after {
    content: '';
    width: 20px;
    height: 20px;
    margin-left: 0.75rem;
    border: 2px solid var(--border-medium);
    border-top-color: var(--accent);
    border-radius: 50%;
    animation: spin 0.8s linear infinite;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}

/* ===== Empty State ===== */
.empty-state {
    text-align: center;
    padding: 4rem 2rem;
    color: var(--text-secondary);
}

.empty-state h2 {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 0.5rem;
}

.empty-state p {
    color: var(--text-muted);
}

/* ===== Responsive Design ===== */

/* Smaller gaps on large screens */
@media (max-width: 1200px) {
    .books-container {
        grid-template-columns: repeat(auto-fit, 150px);
        gap: 1.5rem;
    }
}

/* Smaller gaps on medium-large screens */
@media (max-width: 992px) {
    .books-container {
        grid-template-columns: repeat(auto-fit, 140px);
        gap: 1.5rem;
    }
}

/* 3 columns on tablets */
@media (max-width: 768px) {
    .bookshelf-container {
        padding: 2rem 1.5rem;
    }

    .books-container {
        grid-template-columns: repeat(auto-fit, 120px);
        gap: 1.25rem;
    }


    .modal-content {
        grid-template-columns: 1fr;
        text-align: center;
    }

    .modal-cover {
        display: flex;
        justify-content: center;
    }

    .modal-cover img {
        width: 160px;
    }

    .modal-title {
        padding-right: 0;
    }

    .modal-meta {
        justify-content: center;
    }

    .modal-button {
        align-self: center;
    }
}

/* 2 columns on mobile */
@media (max-width: 480px) {
    .header {
        padding: 2.5rem 1rem 1.5rem;
    }

    .bookshelf-container {
        padding: 1.5rem 1rem;
    }

    .books-container {
        grid-template-columns: repeat(auto-fit, 130px);
        gap: 1rem;
    }


    .modal {
        border-radius: 12px;
    }

    .modal-content {
        padding: 1.5rem;
        gap: 1.5rem;
    }

    .modal-title {
        font-size: 1.25rem;
    }
}

/* ===== Accessibility ===== */
@media (prefers-reduced-motion: reduce) {
    *, *::before, *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
}

.book:focus-visible {
    outline: 2px solid var(--accent);
    outline-offset: 2px;
}

.modal-close:focus-visible {
    outline: 2px solid var(--accent);
    outline-offset: 2px;
}

.modal-button:focus-visible {
    outline: 2px solid var(--accent);
    outline-offset: 2px;
}

/* ===== Theme Toggle Button ===== */
.theme-toggle {
    position: absolute;
    top: 1.5rem;
    right: 1.5rem;
    width: 48px;
    height: 48px;
    border: none;
    border-radius: 50%;
    background: var(--bg-secondary);
    box-shadow: var(--shadow-md);
    cursor: pointer;
    transition: transform 0.2s ease, box-shadow 0.2s ease;
    display: flex;
    align-items: center;
    justify-content: center;
}

.theme-toggle:hover {
    transform: scale(1.1);
    box-shadow: var(--shadow-lg);
}

.theme-toggle-icon {
    width: 24px;
    height: 24px;
    border-radius: 50%;
    background: var(--text-primary);
    position: relative;
    transition: transform 0.3s ease, background 0.3s ease;
}

/* Sun icon (light mode) */
.theme-toggle-icon::before {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    width: 10px;
    height: 10px;
    background: var(--bg-secondary);
    border-radius: 50%;
    transform: translate(-50%, -50%);
    transition: transform 0.3s ease;
}

/* Moon crescent (dark mode) */
[data-theme="dark"] .theme-toggle-icon::before {
    transform: translate(-20%, -50%);
    width: 16px;
    height: 16px;
}

/* ===== Dark Mode Support (class-based) ===== */
[data-theme="dark"] {
    --bg-primary: #1C1917;
    --bg-secondary: #292524;
    --bg-tertiary: #44403C;

    --text-primary: #FAFAF9;
    --text-secondary: #D6D3D1;
    --text-muted: #A8A29E;

    --border-light: #44403C;
    --border-medium: #57534E;

    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.4);
    --shadow-lg: 0 12px 40px rgba(0, 0, 0, 0.5);
    --shadow-xl: 0 25px 60px rgba(0, 0, 0, 0.6);
}

/* Dark mode recessed effect */
[data-theme="dark"] .bookshelf-container {
    background: rgba(0, 0, 0, 0.2);
    box-shadow:
        inset 0 2px 12px rgba(0, 0, 0, 0.3),
        inset 0 1px 3px rgba(0, 0, 0, 0.4),
        inset 0 -2px 0 rgba(255, 255, 255, 0.03);
    border: 1px solid rgba(255, 255, 255, 0.03);
}