/* ===== CSS Variables (Custom Properties) ===== */
:root {
    /* Light Theme Colors */
    --primary-color: #6D4C41; /* Richer espresso brown */
    --primary-hover: #4E342E;
    --bg-color: #FAF8F5; /* Softer parchment cream */
    --bg-alt: #F0EAE1;
    --text-color: #2D2A26; /* Dark text */
    --text-muted: #79736B;
    --glass-bg: rgba(250, 248, 245, 0.75);
    --glass-border: rgba(109, 76, 65, 0.15);
    --shadow: 0 8px 30px rgba(0, 0, 0, 0.08); /* Softer, larger shadow */
    --card-bg: #FFFFFF;
    --accent: #D4AF37; /* Muted gold */
    --error: #D32F2F;
    --success: #388E3C;
    --skeleton-bg: #e0e0e0;
    --skeleton-shine: #f0f0f0;
    
    /* Typography */
    --font-heading: 'Playfair Display', serif;
    --font-body: 'Inter', sans-serif;
    
    /* Spacing */
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 2rem;
    --spacing-lg: 4rem;
    --spacing-xl: 6rem;
    
    /* Transitions */
    --transition-speed: 0.3s;
}

/* Dark Theme Variables */
body.dark-theme {
    --primary-color: #D7CCC8;
    --primary-hover: #EFEBE9;
    --bg-color: #161514; /* Very dark rich warm gray */
    --bg-alt: #22201F;
    --text-color: #F5F5F5;
    --text-muted: #A8A39F;
    --glass-bg: rgba(22, 21, 20, 0.8);
    --glass-border: rgba(215, 204, 200, 0.15);
    --shadow: 0 8px 30px rgba(0, 0, 0, 0.5);
    --card-bg: #1F1D1C;
    --accent: #E5C158;
    --skeleton-bg: #333333;
    --skeleton-shine: #444444;
}

/* ===== Base Styles & Resets ===== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-body);
    background-color: var(--bg-color);
    color: var(--text-color);
    line-height: 1.6;
    transition: background-color var(--transition-speed), color var(--transition-speed);
    overflow-x: hidden;
}

h1, h2, h3, h4, h5, h6 {
    font-family: var(--font-heading);
    font-weight: 600;
    color: var(--text-color);
    margin-bottom: var(--spacing-sm);
}

a {
    color: var(--primary-color);
    text-decoration: none;
    transition: color var(--transition-speed);
}

a:hover {
    color: var(--primary-hover);
}

ul {
    list-style: none;
}

img {
    max-width: 100%;
    height: auto;
    display: block;
}

.container {
    width: 90%;
    max-width: 1200px;
    margin: 0 auto;
}

.section-padding {
    padding: var(--spacing-lg) 0;
}

.bg-alt {
    background-color: var(--bg-alt);
}

.text-center {
    text-align: center;
}

/* ===== Glassmorphism Utilities ===== */
.glass-panel {
    background: var(--glass-bg);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
    border: 1px solid var(--glass-border);
    border-radius: 12px;
    box-shadow: var(--shadow);
}

/* ===== Typography Utilities ===== */
.section-title {
    font-size: 2.5rem;
    text-align: center;
    margin-bottom: var(--spacing-md);
    position: relative;
    padding-bottom: var(--spacing-sm);
}

.section-title::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 50%;
    transform: translateX(-50%);
    width: 60px;
    height: 3px;
    background-color: var(--primary-color);
    border-radius: 2px;
}

/* ===== Buttons ===== */
.btn {
    display: inline-block;
    padding: 0.6rem 1.5rem;
    font-family: var(--font-body);
    font-weight: 500;
    border-radius: 30px;
    cursor: pointer;
    border: none;
    outline: none;
    transition: all var(--transition-speed);
    text-align: center;
}

.btn-primary {
    background-color: var(--primary-color);
    color: #fff;
}

.btn-primary:hover {
    background-color: var(--primary-hover);
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(140, 106, 93, 0.3);
    color: #fff;
}

.btn-outline {
    background-color: transparent;
    border: 1px solid var(--primary-color);
    color: var(--primary-color);
}

.btn-outline:hover {
    background-color: var(--primary-color);
    color: #fff;
}

.btn-large {
    padding: 0.8rem 2rem;
    font-size: 1.1rem;
}

.btn-icon {
    background: none;
    border: none;
    font-size: 1.5rem;
    cursor: pointer;
    color: var(--text-color);
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 0.5rem;
    border-radius: 50%;
    transition: background-color var(--transition-speed);
    position: relative;
}

.btn-icon:hover {
    background-color: var(--bg-alt);
}

.full-width {
    width: 100%;
}

.cart-icon {
    position: relative;
}

.badge {
    position: absolute;
    top: 0;
    right: -5px;
    background-color: var(--error);
    color: white;
    font-size: 0.75rem;
    font-weight: bold;
    border-radius: 50%;
    padding: 2px 6px;
    min-width: 18px;
    text-align: center;
    font-family: var(--font-body);
}

/* ===== Forms ===== */
.input-group {
    margin-bottom: var(--spacing-sm);
    text-align: left;
}

.input-group label {
    display: block;
    margin-bottom: 0.3rem;
    font-weight: 500;
    font-size: 0.9rem;
}

.input-group input, select {
    width: 100%;
    padding: 0.8rem;
    border: 1px solid var(--glass-border);
    border-radius: 8px;
    background-color: var(--card-bg);
    color: var(--text-color);
    font-family: var(--font-body);
    transition: border-color var(--transition-speed), box-shadow var(--transition-speed);
}

.input-group input:focus, select:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(140, 106, 93, 0.1);
}

.error-msg {
    color: var(--error);
    font-size: 0.85rem;
    margin-bottom: var(--spacing-sm);
    min-height: 1.2rem;
}

.success-msg {
    color: var(--success);
    font-size: 0.85rem;
    margin-bottom: var(--spacing-sm);
    min-height: 1.2rem;
}

/* ===== Navbar ===== */
.navbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem 5%;
    position: sticky;
    top: 0;
    z-index: 100;
    background: var(--glass-bg);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--glass-border);
}

.logo h1 {
    margin: 0;
    font-size: 1.8rem;
    color: var(--primary-color);
}

.nav-links {
    display: flex;
    gap: 2rem;
}

.nav-links a {
    color: var(--text-color);
    font-weight: 500;
    position: relative;
}

.nav-links a::after {
    content: '';
    position: absolute;
    bottom: -5px;
    left: 0;
    width: 0;
    height: 2px;
    background-color: var(--primary-color);
    transition: width var(--transition-speed);
}

.nav-links a:hover::after {
    width: 100%;
}

.nav-actions {
    display: flex;
    align-items: center;
    gap: 1rem;
}

#auth-buttons, #user-menu {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.hidden {
    display: none !important;
}

.mobile-only {
    display: none;
}

/* ===== Hero Section ===== */
.hero {
    min-height: 85vh;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    text-align: center;
    padding: 0 5%;
    position: relative;
    overflow: hidden;
    background-image: url('https://images.unsplash.com/photo-1481627834876-b7833e8f5570?auto=format&fit=crop&q=80&w=2000');
    background-size: cover;
    background-position: center;
    background-attachment: fixed;
    color: #FFFFFF;
}

.hero::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: linear-gradient(to bottom, rgba(0,0,0,0.3) 0%, rgba(0,0,0,0.8) 100%);
    z-index: 1;
}

.hero-content, .hero-quote {
    position: relative;
    z-index: 2;
}

.hero-content {
    max-width: 800px;
    margin-bottom: var(--spacing-lg);
}

.hero h1 {
    font-size: 4.5rem;
    line-height: 1.1;
    margin-bottom: var(--spacing-sm);
    color: #FFFFFF;
    text-shadow: 0 4px 10px rgba(0,0,0,0.5);
}

.hero p {
    font-size: 1.25rem;
    color: rgba(255, 255, 255, 0.85);
    margin-bottom: var(--spacing-md);
    text-shadow: 0 2px 5px rgba(0,0,0,0.5);
}

.hero-quote {
    max-width: 600px;
    margin: 0 auto;
    padding: 2rem;
    border-left: 4px solid var(--accent);
    background-color: rgba(0, 0, 0, 0.4);
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px);
    border-radius: 0 12px 12px 0;
    text-align: left;
    box-shadow: 0 10px 30px rgba(0,0,0,0.5);
}

.hero-quote blockquote {
    font-family: var(--font-heading);
    font-style: italic;
    font-size: 1.3rem;
    margin-bottom: 0.5rem;
    color: #FFF;
}

.hero-quote cite {
    font-size: 0.9rem;
    color: var(--accent);
    font-weight: 600;
}

/* ===== Dashboard Stats ===== */
.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 2rem;
}

.stat-card {
    padding: 2rem;
    text-align: center;
    transition: transform var(--transition-speed);
}

.stat-card:hover {
    transform: translateY(-5px);
}

.stat-title {
    font-family: var(--font-body);
    font-size: 1rem;
    color: var(--text-muted);
    font-weight: 500;
}

.stat-value {
    font-family: var(--font-heading);
    font-size: 3rem;
    color: var(--primary-color);
    font-weight: 700;
}

/* ===== Library Section ===== */
.library-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: var(--spacing-md);
    flex-wrap: wrap;
    gap: 1rem;
}

.search-bar input {
    width: 300px;
    padding: 0.8rem 1rem;
    border-radius: 30px;
    border: 1px solid var(--glass-border);
    background-color: var(--card-bg);
    color: var(--text-color);
    box-shadow: var(--shadow);
}

.library-layout {
    display: grid;
    grid-template-columns: 250px 1fr;
    gap: 2rem;
}

.sidebar {
    padding: 1.5rem;
    height: fit-content;
    position: sticky;
    top: 100px;
}

.filter-group {
    margin-bottom: 1.5rem;
}

.filter-group h4 {
    font-size: 1rem;
    margin-bottom: 0.5rem;
    color: var(--text-muted);
}

/* Book Grid */
.books-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
    gap: 2.5rem;
}

/* Bestseller Badge */
.badge-bestseller {
    position: absolute;
    top: 20px;
    left: -35px;
    background: var(--accent);
    color: #111;
    padding: 6px 40px;
    font-size: 0.75rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 1.5px;
    transform: rotate(-45deg);
    z-index: 10;
    box-shadow: 0 4px 15px rgba(0,0,0,0.3);
}

/* Book Card */
.book-card {
    background: var(--card-bg);
    border-radius: 12px;
    overflow: hidden;
    box-shadow: var(--shadow);
    transition: transform var(--transition-speed), box-shadow var(--transition-speed);
    position: relative;
    display: flex;
    flex-direction: column;
    border: 1px solid var(--glass-border);
}

.book-card:hover {
    transform: translateY(-8px);
    box-shadow: 0 12px 24px rgba(0,0,0,0.1);
}

.book-cover {
    height: 320px;
    overflow: hidden;
    position: relative;
    cursor: pointer;
}

.book-cover img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    transition: transform 0.5s ease;
}

.book-card:hover .book-cover img {
    transform: scale(1.05);
}

.book-overlay {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0,0,0,0.4);
    display: flex;
    justify-content: center;
    align-items: center;
    opacity: 0;
    transition: opacity var(--transition-speed);
}

.book-card:hover .book-overlay {
    opacity: 1;
}

.book-info {
    padding: 1.2rem;
    flex-grow: 1;
    display: flex;
    flex-direction: column;
}

.book-genre {
    font-size: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 1px;
    color: var(--primary-color);
    font-weight: 600;
    margin-bottom: 0.3rem;
}

.book-title {
    font-size: 1.1rem;
    margin-bottom: 0.2rem;
    line-height: 1.3;
    cursor: pointer;
    transition: color 0.2s;
}
.book-title:hover {
    color: var(--primary-hover);
}

.book-author {
    font-size: 0.9rem;
    color: var(--text-muted);
    margin-bottom: 0.8rem;
}

.book-meta {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1rem;
}

.book-rating {
    color: var(--accent);
    font-size: 0.9rem;
}

.book-price {
    font-weight: 600;
    color: var(--text-color);
}

.book-actions {
    margin-top: auto;
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 0.5rem;
}

.btn-add-cart {
    flex-grow: 1;
    padding: 0.5rem;
    font-size: 0.9rem;
}

.btn-fav {
    background: none;
    border: none;
    font-size: 1.5rem;
    cursor: pointer;
    color: #ccc;
    transition: color 0.2s, transform 0.2s;
}

.btn-fav:hover {
    transform: scale(1.1);
}

.btn-fav.active {
    color: #e25555; /* heart red */
}

/* Progress bar inside book card */
.progress-container {
    margin-top: 1rem;
    border-top: 1px solid var(--glass-border);
    padding-top: 0.8rem;
}

.progress-bar {
    width: 100%;
    height: 6px;
    background-color: var(--bg-alt);
    border-radius: 3px;
    overflow: hidden;
    margin-bottom: 0.3rem;
}

.progress-fill {
    height: 100%;
    background-color: var(--primary-color);
    width: 0%;
    transition: width 0.5s ease-out;
}

.progress-text {
    font-size: 0.75rem;
    color: var(--text-muted);
    text-align: right;
    display: block;
}

.progress-controls {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    margin-top: 0.5rem;
}

.progress-controls input[type="range"] {
    flex-grow: 1;
    accent-color: var(--primary-color);
}

/* ===== Modal Utilities ===== */
.modal {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.6);
    backdrop-filter: blur(5px);
    display: flex;
    justify-content: center;
    align-items: center;
    z-index: 1000;
    opacity: 1;
    transition: opacity var(--transition-speed);
}

.modal.hidden {
    opacity: 0;
    pointer-events: none;
}

.modal-content {
    background-color: var(--card-bg);
    padding: 2.5rem;
    width: 90%;
    max-width: 400px;
    position: relative;
    transform: translateY(0);
    transition: transform var(--transition-speed);
    max-height: 90vh;
    overflow-y: auto;
}

.modal-content.large-modal {
    max-width: 800px;
    padding: 2rem;
}

.modal.hidden .modal-content {
    transform: translateY(-20px);
}

.close-btn {
    position: absolute;
    top: 1rem;
    right: 1.5rem;
    font-size: 1.5rem;
    cursor: pointer;
    color: var(--text-muted);
    z-index: 10;
}

.close-btn:hover {
    color: var(--error);
}

.switch-auth {
    text-align: center;
    margin-top: 1.5rem;
    font-size: 0.9rem;
}

/* ===== Cart Modal Specifics ===== */
.cart-modal-content {
    max-width: 500px;
    display: flex;
    flex-direction: column;
}

.cart-items {
    margin: 1.5rem 0;
    display: flex;
    flex-direction: column;
    gap: 1rem;
    flex-grow: 1;
}

.cart-empty {
    text-align: center;
    color: var(--text-muted);
    padding: 2rem 0;
}

.cart-item {
    display: flex;
    align-items: center;
    gap: 1rem;
    padding-bottom: 1rem;
    border-bottom: 1px solid var(--glass-border);
}

.cart-item-img {
    width: 60px;
    height: 85px;
    object-fit: cover;
    border-radius: 4px;
}

.cart-item-details {
    flex-grow: 1;
}

.cart-item-title {
    font-weight: 600;
    font-size: 1rem;
    margin-bottom: 0.2rem;
}

.cart-item-price {
    color: var(--text-muted);
    font-size: 0.9rem;
}

.cart-item-actions {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.qty-btn {
    background: var(--bg-alt);
    border: none;
    width: 25px;
    height: 25px;
    border-radius: 4px;
    cursor: pointer;
    color: var(--text-color);
}

.qty-input {
    width: 30px;
    text-align: center;
    border: none;
    background: transparent;
    color: var(--text-color);
    font-family: var(--font-body);
}

.cart-item-remove {
    background: none;
    border: none;
    color: var(--error);
    cursor: pointer;
    font-size: 1.2rem;
    margin-left: 0.5rem;
}

.cart-footer {
    border-top: 2px solid var(--glass-border);
    padding-top: 1rem;
    margin-top: auto;
}

.cart-total {
    font-size: 1.2rem;
    font-weight: bold;
    display: flex;
    justify-content: space-between;
    margin-bottom: 1rem;
}

/* ===== Book Details Modal Specifics ===== */
.book-details-layout {
    display: grid;
    grid-template-columns: 1fr 1.5fr;
    gap: 2rem;
}

.detail-img-container {
    width: 100%;
}
.detail-img-container img {
    border-radius: 8px;
    box-shadow: var(--shadow);
}

.detail-info h2 {
    font-size: 2rem;
    margin-bottom: 0.5rem;
}

.detail-author {
    font-size: 1.1rem;
    color: var(--text-muted);
    margin-bottom: 1rem;
}

.detail-meta {
    display: flex;
    gap: 1rem;
    margin-bottom: 1.5rem;
    font-size: 0.9rem;
}

.detail-price {
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--primary-color);
    margin: 1.5rem 0;
}

.detail-desc {
    line-height: 1.7;
    margin-bottom: 2rem;
}

.detail-reviews {
    margin-top: 2rem;
    border-top: 1px solid var(--glass-border);
    padding-top: 1rem;
}

.detail-reviews h4 {
    margin-bottom: 1rem;
}

.review-item {
    background: var(--bg-alt);
    padding: 1rem;
    border-radius: 8px;
    margin-bottom: 1rem;
    font-style: italic;
    font-size: 0.9rem;
}

/* ===== Loading Skeletons ===== */
@keyframes shimmer {
    0% { background-position: -400px 0; }
    100% { background-position: 400px 0; }
}

.skeleton {
    background: linear-gradient(90deg, var(--skeleton-bg) 25%, var(--skeleton-shine) 50%, var(--skeleton-bg) 75%);
    background-size: 400px 100%;
    animation: shimmer 1.5s infinite linear;
    border-radius: 4px;
}

.skeleton-card {
    height: 450px;
    border-radius: 12px;
}

/* ===== Testimonials ===== */
.testimonial-slider {
    max-width: 800px;
    margin: 0 auto;
    position: relative;
    padding: 2rem;
}

.testimonial-card {
    display: none;
    animation: fadeIn 0.5s ease;
}

.testimonial-card.active {
    display: block;
}

.testimonial-text {
    font-size: 1.2rem;
    font-style: italic;
    margin-bottom: 1rem;
}

.testimonial-author {
    font-weight: 600;
    color: var(--primary-color);
}

/* ===== Footer ===== */
footer {
    background-color: var(--bg-alt);
    padding: 3rem 0 1rem;
    margin-top: var(--spacing-lg);
    border-top: 1px solid var(--glass-border);
}

.footer-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    margin-bottom: 2rem;
    gap: 2rem;
}

.footer-brand h2 {
    color: var(--primary-color);
    margin-bottom: 0.5rem;
}

.footer-links {
    display: flex;
    gap: 1.5rem;
}

.footer-socials {
    display: flex;
    gap: 1rem;
}

.social-icon {
    font-size: 1.5rem;
    color: var(--text-muted);
    transition: color var(--transition-speed), transform var(--transition-speed);
}

.social-icon:hover {
    color: var(--primary-color);
    transform: translateY(-3px);
}

.footer-bottom {
    text-align: center;
    padding-top: 1.5rem;
    border-top: 1px solid var(--glass-border);
    font-size: 0.9rem;
    color: var(--text-muted);
}