/* Global Styles */
:root {
    --primary-color: #4a90e2;
    --secondary-color: #f0f0f0;
    --accent-color: #e74c3c;
    --text-color: #333;
    --light-text: #fff;
    --dark-text: #222;
    --border-color: #ddd;
    --success-color: #27ae60;
    --shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
}

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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    line-height: 1.6;
    color: var(--text-color);
    background-color: #f9f9f9;
}

a {
    text-decoration: none;
    color: inherit;
}

ul {
    list-style: none;
}

/* Header & Navigation */
header {
    background-color: #fff;
    box-shadow: var(--shadow);
    position: sticky;
    top: 0;
    z-index: 100;
}

.main-nav {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem 5%;
    max-width: 1200px;
    margin: 0 auto;
}

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

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

.nav-links a {
    color: var(--text-color);
    font-weight: 500;
    transition: color 0.3s;
}

.nav-links a:hover,
.nav-links a.active {
    color: var(--primary-color);
}

/* Hero Section */
.hero {
    background: linear-gradient(135deg, var(--primary-color), #2c3e50);
    color: var(--light-text);
    text-align: center;
    padding: 4rem 1rem;
}

.hero-content {
    max-width: 800px;
    margin: 0 auto;
}

.hero h1 {
    font-size: 2.5rem;
    margin-bottom: 1rem;
}

.hero p {
    font-size: 1.2rem;
    opacity: 0.9;
}

/* Book Grid */
.book-grid {
    max-width: 1200px;
    margin: 3rem auto;
    padding: 0 1rem;
}

.book-grid h2 {
    text-align: center;
    margin-bottom: 2rem;
    color: var(--dark-text);
    position: relative;
    padding-bottom: 0.5rem;
}

.book-grid h2:after {
    content: "";
    position: absolute;
    bottom: 0;
    left: 50%;
    transform: translateX(-50%);
    width: 60px;
    height: 3px;
    background-color: var(--primary-color);
}

.grid-container {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
    gap: 2rem;
}

.book-card {
    background-color: #fff;
    border-radius: 8px;
    overflow: hidden;
    box-shadow: var(--shadow);
    transition: transform 0.3s, box-shadow 0.3s;
}

.book-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.15);
}

.book-cover {
    position: relative;
    height: 280px;
    overflow: hidden;
}

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

.price-tag {
    position: absolute;
    bottom: 0;
    left: 0;
    right: 0;
    background: rgba(0, 0, 0, 0.7);
    padding: 0.5rem;
    color: var(--light-text);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.original-price {
    text-decoration: line-through;
    opacity: 0.8;
}

.free-label {
    font-weight: bold;
    color: var(--accent-color);
    background-color: rgba(255, 255, 255, 0.9);
    padding: 0.2rem 0.5rem;
    border-radius: 3px;
}

.book-info {
    padding: 1rem;
}

.book-info h3 {
    margin-bottom: 0.5rem;
    font-size: 1.1rem;
    color: var(--dark-text);
}

.author {
    color: #666;
    font-size: 0.9rem;
}

/* Book Detail Page */
.book-detail {
    max-width: 1000px;
    margin: 2rem auto;
    padding: 1rem;
    background-color: #fff;
    border-radius: 8px;
    box-shadow: var(--shadow);
}

.book-header {
    display: flex;
    flex-direction: column;
    gap: 2rem;
    margin-bottom: 2rem;
    border-bottom: 1px solid var(--border-color);
    padding-bottom: 2rem;
}

@media (min-width: 768px) {
    .book-header {
        flex-direction: row;
    }
}

.book-image {
    flex: 0 0 250px;
}

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

.book-header-info {
    flex: 1;
}

.book-title {
    font-size: 2rem;
    margin-bottom: 0.5rem;
    color: var(--dark-text);
}

.book-meta {
    margin-bottom: 1rem;
    color: #555;
}

.book-price {
    display: flex;
    align-items: baseline;
    gap: 1rem;
    margin: 1.5rem 0;
}

.book-price .original-price {
    font-size: 1.2rem;
    color: #777;
}

.book-price .free-label {
    font-size: 1.5rem;
    background-color: var(--success-color);
    color: white;
    padding: 0.3rem 0.8rem;
    border-radius: 4px;
}

.download-btn {
    display: inline-block;
    background-color: var(--primary-color);
    color: var(--light-text);
    padding: 0.8rem 1.5rem;
    border-radius: 5px;
    font-weight: bold;
    transition: background-color 0.3s;
    margin-top: 1rem;
    text-align: center;
}

.download-btn:hover {
    background-color: #3a7bc8;
}

.book-description,
.reader-suitability,
.book-details {
    margin-bottom: 2rem;
}

.section-title {
    font-size: 1.5rem;
    margin-bottom: 1rem;
    color: var(--dark-text);
    border-bottom: 2px solid var(--primary-color);
    padding-bottom: 0.5rem;
    display: inline-block;
}

.suitability-list {
    display: grid;
    grid-template-columns: 1fr;
    gap: 1rem;
}

@media (min-width: 768px) {
    .suitability-list {
        grid-template-columns: 1fr 1fr;
    }
}

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

.suitability-item i {
    color: var(--primary-color);
}

.book-details-grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: 0.5rem;
}

@media (min-width: 768px) {
    .book-details-grid {
        grid-template-columns: 1fr 1fr;
    }
}

.detail-item {
    display: flex;
    gap: 0.5rem;
    padding: 0.5rem 0;
    border-bottom: 1px solid var(--border-color);
}

.detail-label {
    font-weight: bold;
    min-width: 120px;
}

/* Modal for Content Lock */
.modal {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.7);
    z-index: 1000;
    justify-content: center;
    align-items: center;
}

.modal-content {
    background-color: #fff;
    padding: 2rem;
    border-radius: 8px;
    width: 90%;
    max-width: 500px;
    text-align: center;
}

.modal-title {
    color: var(--dark-text);
    margin-bottom: 1rem;
}

.modal-subtitle {
    margin-bottom: 1.5rem;
    color: #666;
}

.social-buttons {
    display: flex;
    justify-content: center;
    gap: 1rem;
    margin-bottom: 1.5rem;
}

.social-btn {
    padding: 0.8rem 1.2rem;
    border-radius: 5px;
    font-weight: bold;
    color: var(--light-text);
    display: flex;
    align-items: center;
    gap: 0.5rem;
    transition: opacity 0.3s;
}

.social-btn:hover {
    opacity: 0.9;
}

.facebook-btn {
    background-color: #3b5998;
}

.twitter-btn {
    background-color: #1da1f2;
}

.close-modal {
    margin-top: 1rem;
    color: #666;
    cursor: pointer;
    transition: color 0.3s;
}

.close-modal:hover {
    color: var(--accent-color);
}

/* Footer */
footer {
    background-color: #222;
    color: var(--light-text);
    padding: 3rem 1rem 1rem;
}

.footer-content {
    display: grid;
    grid-template-columns: 1fr;
    gap: 2rem;
    max-width: 1200px;
    margin: 0 auto;
}

@media (min-width: 768px) {
    .footer-content {
        grid-template-columns: repeat(3, 1fr);
    }
}

.footer-section h3 {
    margin-bottom: 1rem;
    color: var(--primary-color);
}

.footer-section ul li {
    margin-bottom: 0.5rem;
}

.footer-section a {
    color: #ccc;
    transition: color 0.3s;
}

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

.social-icons {
    display: flex;
    gap: 1rem;
    margin-top: 1rem;
}

.social-icons a {
    color: var(--light-text);
    font-size: 1.2rem;
    transition: color 0.3s;
}

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

.footer-bottom {
    max-width: 1200px;
    margin: 0 auto;
    text-align: center;
    padding-top: 2rem;
    margin-top: 2rem;
    border-top: 1px solid #444;
    color: #999;
    font-size: 0.9rem;
}

/* Responsive Adjustments */
@media (max-width: 767px) {
    .main-nav {
        flex-direction: column;
        padding: 1rem;
    }
    
    .nav-links {
        margin-top: 1rem;
        justify-content: center;
        flex-wrap: wrap;
    }
    
    .hero h1 {
        font-size: 2rem;
    }
    
    .grid-container {
        grid-template-columns: repeat(auto-fill, minmax(160px, 1fr));
    }
    
    .book-cover {
        height: 220px;
    }
}