/* style.css - Premium Redesign */
:root {
    --primary-color: #2c3e50;
    --accent-color: #3498db;
    --bg-color: #f4f7f6;
    --text-color: #333333;
    --white: #ffffff;
    --shadow-sm: 0 2px 4px rgba(0, 0, 0, 0.08);
    --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.12);
    --shadow-lg: 0 12px 28px rgba(0, 0, 0, 0.15);
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    --border-radius: 12px;
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html {
    scroll-behavior: smooth;
}

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

/* ========== HEADER & NAVIGATION ========== */

header {
    background: linear-gradient(135deg, var(--primary-color) 0%, #34495e 100%);
    color: var(--white);
    padding: 0;
    box-shadow: var(--shadow-md);
    position: sticky;
    top: 0;
    z-index: 100;
}

.nav-container {
    max-width: 1400px;
    margin: 0 auto;
    padding: 1.2rem 20px;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    font-size: 1.4rem;
    font-weight: 700;
    letter-spacing: -0.5px;
    color: var(--white);
    text-decoration: none;
    transition: var(--transition);
    display: flex;
    align-items: center;
    gap: 8px;
}

.logo:hover {
    opacity: 0.9;
    transform: translateY(-2px);
}

/* Desktop Navigation */
nav ul {
    list-style: none;
    display: flex;
    gap: 32px;
    align-items: center;
}

nav a {
    color: var(--white);
    text-decoration: none;
    font-weight: 500;
    font-size: 0.95rem;
    transition: var(--transition);
    padding: 8px 12px;
    border-radius: 6px;
    position: relative;
}

nav a::after {
    content: '';
    position: absolute;
    bottom: -4px;
    left: 12px;
    width: 0;
    height: 2px;
    background-color: var(--accent-color);
    transition: width 0.3s ease;
}

nav a:hover::after {
    width: calc(100% - 24px);
}

nav a.active-link,
nav a.active-link::after {
    color: var(--accent-color);
}

nav a.active-link::after {
    width: calc(100% - 24px);
}

nav a:hover {
    background-color: rgba(52, 152, 219, 0.15);
}

/* Mobile Menu Button */
.menu-toggle {
    display: none;
    flex-direction: column;
    gap: 6px;
    background: none;
    border: none;
    cursor: pointer;
    padding: 8px;
    align-items: center;
}

.menu-toggle span {
    width: 24px;
    height: 2px;
    background-color: var(--white);
    border-radius: 2px;
    transition: var(--transition);
    display: block;
}

.menu-toggle.active span:nth-child(1) {
    transform: rotate(45deg) translate(10px, 10px);
}

.menu-toggle.active span:nth-child(2) {
    opacity: 0;
}

.menu-toggle.active span:nth-child(3) {
    transform: rotate(-45deg) translate(7px, -7px);
}

/* ========== MAIN CONTENT ========== */

main {
    max-width: 1400px;
    margin: 0 auto;
    padding: 0 20px;
    flex: 1;
    width: 100%;
}

/* Hero Section */
.hero-section {
    background: linear-gradient(135deg, var(--primary-color) 0%, #34495e 100%);
    color: var(--white);
    padding: 4rem 2rem;
    border-radius: var(--border-radius);
    margin: 2rem 0;
    text-align: center;
}

.hero-content h1 {
    color: var(--white);
    font-size: 2.8rem;
    margin-bottom: 1rem;
}

.hero-subtitle {
    font-size: 1.2rem;
    opacity: 0.95;
    line-height: 1.6;
}

/* Page Header */
.page-header {
    padding: 2rem 0;
    margin-bottom: 2rem;
    border-bottom: 2px solid rgba(52, 152, 219, 0.2);
}

.page-header h1 {
    margin-bottom: 0.5rem;
}

.page-header p {
    font-size: 1.05rem;
    color: #666;
}

/* Category Grid */
.categories-section {
    margin: 3rem 0;
}

.category-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 24px;
    margin-top: 2rem;
}

.category-card {
    background: var(--white);
    padding: 32px 24px;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-sm);
    border: 1px solid rgba(0, 0, 0, 0.05);
    transition: var(--transition);
    text-align: center;
    display: flex;
    flex-direction: column;
    align-items: center;
}

.category-card:hover {
    transform: translateY(-6px);
    box-shadow: var(--shadow-lg);
    border-color: rgba(52, 152, 219, 0.15);
}

.category-icon {
    font-size: 3rem;
    margin-bottom: 16px;
    display: block;
}

.category-card h3 {
    margin-bottom: 12px;
    font-size: 1.4rem;
}

.category-card p {
    color: #666;
    margin-bottom: 20px;
    flex-grow: 1;
    font-size: 0.95rem;
    line-height: 1.6;
}

/* About Section */
.about-content {
    padding: 1rem 0;
}

.about-item {
    margin-bottom: 2rem;
}

.about-item h3 {
    margin-top: 0;
    margin-bottom: 0.25rem;
}

.author-info {
    color: var(--accent-color);
    font-weight: 600;
    font-size: 0.9rem;
    margin-bottom: 1rem;
}

/* Loading and Error States */
.loading-state,
.error-state {
    text-align: center;
    padding: 3rem 2rem;
    color: #888;
    font-size: 1.05rem;
}

.error-state {
    color: #d32f2f;
}

h1 {
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--primary-color);
    margin-bottom: 1.5rem;
    letter-spacing: -1px;
}

h2 {
    font-size: 2rem;
    font-weight: 700;
    color: var(--primary-color);
    margin-bottom: 1.5rem;
    letter-spacing: -0.5px;
}

h3 {
    font-size: 1.3rem;
    font-weight: 600;
    color: var(--primary-color);
    margin-bottom: 1rem;
}

/* ========== BOOK GRID & CARDS ========== */

.book-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
    gap: 28px;
    margin-top: 30px;
}

.book-card {
    background: var(--white);
    padding: 28px;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-sm);
    transition: var(--transition);
    display: flex;
    flex-direction: column;
    justify-content: space-between;
    border: 1px solid rgba(0, 0, 0, 0.05);
    overflow: hidden;
    position: relative;
}

.book-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 4px;
    background: linear-gradient(90deg, var(--accent-color), #2980b9);
}

.book-card:hover {
    transform: translateY(-8px);
    box-shadow: var(--shadow-lg);
    border-color: rgba(52, 152, 219, 0.2);
}

.book-title {
    font-size: 1.2rem;
    font-weight: 600;
    margin-bottom: 12px;
    color: var(--primary-color);
    line-height: 1.4;
}

.book-description {
    font-size: 0.95rem;
    color: #666;
    margin-bottom: 16px;
    flex-grow: 1;
    line-height: 1.6;
}

.book-meta {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 20px;
    font-size: 0.85rem;
    color: #888;
}

/* ========== BUTTONS ========== */

.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    background: linear-gradient(135deg, var(--accent-color) 0%, #2980b9 100%);
    color: var(--white);
    padding: 12px 24px;
    text-decoration: none;
    border-radius: 8px;
    text-align: center;
    transition: var(--transition);
    margin-top: auto;
    font-weight: 600;
    font-size: 0.95rem;
    border: none;
    cursor: pointer;
    box-shadow: 0 4px 15px rgba(52, 152, 219, 0.3);
    position: relative;
    overflow: hidden;
}

.btn::before {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    width: 0;
    height: 0;
    background: rgba(255, 255, 255, 0.3);
    border-radius: 50%;
    transform: translate(-50%, -50%);
    transition: width 0.6s, height 0.6s;
}

.btn:hover::before {
    width: 300px;
    height: 300px;
}

.btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(52, 152, 219, 0.4);
}

.btn:active {
    transform: translateY(0);
    box-shadow: 0 2px 10px rgba(52, 152, 219, 0.3);
}

/* Button Variants */
.btn-secondary {
    background: linear-gradient(135deg, #ecf0f1 0%, #bdc3c7 100%);
    color: var(--primary-color);
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.1);
}

.btn-secondary:hover {
    box-shadow: 0 6px 20px rgba(0, 0, 0, 0.15);
}

.btn-small {
    padding: 8px 16px;
    font-size: 0.85rem;
}

.btn-large {
    padding: 16px 32px;
    font-size: 1.05rem;
}

/* ========== SECTION CARDS ========== */

.section-card {
    background: var(--white);
    padding: 40px;
    margin-bottom: 40px;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-sm);
    border: 1px solid rgba(0, 0, 0, 0.05);
    transition: var(--transition);
}

.section-card:hover {
    box-shadow: var(--shadow-md);
    border-color: rgba(52, 152, 219, 0.15);
}

.section-card h2 {
    margin-top: 0;
}

/* ========== FOOTER ========== */

footer {
    background: linear-gradient(135deg, var(--primary-color) 0%, #34495e 100%);
    color: var(--white);
    text-align: center;
    padding: 2.5rem 20px;
    margin-top: auto;
    border-top: 1px solid rgba(255, 255, 255, 0.1);
}

footer p {
    font-size: 0.95rem;
    opacity: 0.95;
}

/* ========== UTILITIES ========== */

.container {
    max-width: 1400px;
    margin: 0 auto;
    padding: 0 20px;
}

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

.mt-3 {
    margin-top: 2rem;
}

.mb-3 {
    margin-bottom: 2rem;
}

/* ========== RESPONSIVE DESIGN ========== */

@media (max-width: 992px) {
    h1 {
        font-size: 2rem;
    }

    h2 {
        font-size: 1.6rem;
    }

    .book-grid {
        grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
        gap: 24px;
    }

    .category-grid {
        grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
        gap: 20px;
    }

    .hero-section {
        padding: 3rem 1.5rem;
    }

    .hero-content h1 {
        font-size: 2.2rem;
    }

    .hero-subtitle {
        font-size: 1.05rem;
    }
}

@media (max-width: 768px) {
    /* Mobile Navigation */
    nav ul {
        position: absolute;
        top: 100%;
        left: 0;
        right: 0;
        flex-direction: column;
        gap: 0;
        background: rgba(44, 62, 80, 0.98);
        max-height: 0;
        overflow: hidden;
        transition: max-height 0.4s ease;
        padding: 0;
    }

    nav ul.active {
        max-height: 400px;
        padding: 12px 0;
    }

    nav li {
        width: 100%;
    }

    nav a {
        display: block;
        padding: 16px 24px;
        border-radius: 0;
        border-bottom: 1px solid rgba(255, 255, 255, 0.1);
    }

    nav a::after {
        display: none;
    }

    nav a:hover {
        background-color: rgba(52, 152, 219, 0.25);
        padding-left: 32px;
    }

    nav a.active-link {
        background-color: rgba(52, 152, 219, 0.3);
        color: var(--accent-color);
    }

    .menu-toggle {
        display: flex;
    }

    .nav-container {
        position: relative;
        flex-wrap: wrap;
        padding: 1rem 20px;
    }

    header {
        position: sticky;
        top: 0;
    }

    h1 {
        font-size: 1.8rem;
    }

    h2 {
        font-size: 1.4rem;
    }

    .hero-section {
        padding: 2.5rem 1.5rem;
        margin: 1.5rem 0;
    }

    .hero-content h1 {
        font-size: 1.8rem;
    }

    .hero-subtitle {
        font-size: 1rem;
    }

    .category-grid {
        grid-template-columns: 1fr;
    }

    .category-card {
        padding: 24px 20px;
    }

    .book-grid {
        grid-template-columns: 1fr;
        gap: 20px;
    }

    .section-card {
        padding: 24px;
        margin-bottom: 24px;
    }

    .btn {
        width: 100%;
        padding: 14px 24px;
    }

    main {
        margin: 0 auto;
        padding: 0 16px;
    }

    footer {
        padding: 2rem 20px;
    }

    .page-header {
        padding: 1.5rem 0;
    }
}

@media (max-width: 480px) {
    :root {
        --border-radius: 10px;
    }

    .logo {
        font-size: 1.2rem;
    }

    h1 {
        font-size: 1.5rem;
        margin-bottom: 1rem;
    }

    h2 {
        font-size: 1.2rem;
    }

    .hero-content h1 {
        font-size: 1.5rem;
    }

    .hero-subtitle {
        font-size: 0.95rem;
    }

    .category-card {
        padding: 20px;
    }

    .category-icon {
        font-size: 2.5rem;
    }

    .book-card {
        padding: 20px;
    }

    .section-card {
        padding: 20px;
    }

    main {
        margin: 0 auto;
    }

    nav a {
        padding: 14px 20px;
    }

    nav a:hover {
        padding-left: 28px;
    }

    .btn {
        padding: 12px 20px;
        font-size: 0.9rem;
    }
}

/* ========== ANIMATIONS ========== */

@keyframes slideInDown {
    from {
        opacity: 0;
        transform: translateY(-20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes fadeIn {
    from {
        opacity: 0;
    }
    to {
        opacity: 1;
    }
}

.book-card {
    animation: fadeIn 0.5s ease forwards;
}

.book-card:nth-child(1) {
    animation-delay: 0.1s;
}

.book-card:nth-child(2) {
    animation-delay: 0.2s;
}

.book-card:nth-child(3) {
    animation-delay: 0.3s;
}

.book-card:nth-child(4) {
    animation-delay: 0.4s;
}

.book-card:nth-child(5) {
    animation-delay: 0.5s;
}

.book-card:nth-child(6) {
    animation-delay: 0.6s;
}