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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    line-height: 1.6;
    color: #333;
    background-color: #f5f5f5;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 20px;
}

header {
    text-align: center;
    margin-bottom: 40px;
    padding: 30px 0;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    border-radius: 10px;
}

header h1 {
    font-size: 2.5rem;
    margin-bottom: 10px;
}

.subtitle {
    font-size: 1.1rem;
    opacity: 0.9;
}

.actions {
    display: flex;
    gap: 15px;
    justify-content: center;
    margin-bottom: 30px;
}

.btn {
    padding: 12px 24px;
    font-size: 1rem;
    border: none;
    border-radius: 6px;
    cursor: pointer;
    transition: all 0.3s ease;
    font-weight: 500;
}

.btn-primary {
    background-color: #667eea;
    color: white;
}

.btn-primary:hover {
    background-color: #5568d3;
    transform: translateY(-2px);
}

.btn-secondary {
    background-color: #764ba2;
    color: white;
}

.btn-secondary:hover {
    background-color: #643a8a;
    transform: translateY(-2px);
}

.message {
    padding: 15px 20px;
    border-radius: 6px;
    margin-bottom: 20px;
    text-align: center;
}

.message.success {
    background-color: #d4edda;
    color: #155724;
    border: 1px solid #c3e6cb;
}

.message.error {
    background-color: #f8d7da;
    color: #721c24;
    border: 1px solid #f5c6cb;
}

.message.hidden {
    display: none;
}

.section {
    background: white;
    padding: 30px;
    border-radius: 10px;
    margin-bottom: 30px;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
}

.section h2 {
    font-size: 1.8rem;
    margin-bottom: 20px;
    color: #667eea;
}

.recommendations-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 20px;
}

.recommendation-card {
    background: #f9f9f9;
    padding: 20px;
    border-radius: 8px;
    border: 1px solid #e0e0e0;
    transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.recommendation-card:hover {
    transform: translateY(-4px);
    box-shadow: 0 4px 12px rgba(0,0,0,0.15);
}

.recommendation-card h3 {
    font-size: 1.3rem;
    margin-bottom: 5px;
    color: #333;
}

.author {
    color: #666;
    font-style: italic;
    margin-bottom: 10px;
}

.description {
    margin-bottom: 15px;
    line-height: 1.5;
}

.reason {
    background: #fff;
    padding: 10px;
    border-left: 3px solid #667eea;
    margin-bottom: 10px;
}

.reason strong {
    color: #667eea;
}

.reason p {
    margin-top: 5px;
    font-size: 0.95rem;
}

.genres {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    margin-top: 10px;
}

.genre-tag {
    background: #667eea;
    color: white;
    padding: 4px 12px;
    border-radius: 20px;
    font-size: 0.85rem;
}

.history-list {
    display: flex;
    flex-direction: column;
    gap: 15px;
}

.history-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 15px;
    background: #f9f9f9;
    border-radius: 8px;
    border: 1px solid #e0e0e0;
}

.book-info h3 {
    font-size: 1.1rem;
    margin-bottom: 5px;
}

.status {
    padding: 6px 12px;
    border-radius: 20px;
    font-size: 0.9rem;
    font-weight: 500;
}

.status.finished {
    background-color: #d4edda;
    color: #155724;
}

.status.in-progress {
    background-color: #fff3cd;
    color: #856404;
}

.empty-state {
    text-align: center;
    color: #999;
    padding: 40px;
    font-size: 1.1rem;
}

/* ==================== Navigation ====================*/

.navbar {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 0;
    margin-bottom: 20px;
    box-shadow: 0 2px 8px rgba(0,0,0,0.1);
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 15px 20px;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.nav-brand a {
    color: white;
    text-decoration: none;
    font-size: 1.3rem;
    font-weight: 600;
}

.nav-links {
    display: flex;
    list-style: none;
    gap: 30px;
}

.nav-links a {
    color: white;
    text-decoration: none;
    transition: opacity 0.3s ease;
}

.nav-links a:hover {
    opacity: 0.8;
}

.nav-user {
    display: flex;
    align-items: center;
    gap: 15px;
}

.user-name {
    font-weight: 500;
}

.btn-text {
    background: transparent;
    color: white;
    border: 1px solid rgba(255,255,255,0.3);
    padding: 8px 16px;
}

.btn-text:hover {
    background: rgba(255,255,255,0.1);
}


/* ==================== Authentication Pages ====================*/

.auth-container {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 20px;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
}

.auth-card {
    background: white;
    padding: 40px;
    border-radius: 12px;
    box-shadow: 0 8px 24px rgba(0,0,0,0.15);
    max-width: 480px;
    width: 100%;
}

.auth-card h1 {
    text-align: center;
    color: #333;
    margin-bottom: 10px;
    font-size: 2rem;
}

.auth-subtitle {
    text-align: center;
    color: #666;
    margin-bottom: 30px;
}

.form-group {
    margin-bottom: 20px;
}

.form-group label {
    display: block;
    margin-bottom: 8px;
    color: #333;
    font-weight: 500;
}

.form-group input {
    width: 100%;
    padding: 12px;
    border: 1px solid #ddd;
    border-radius: 6px;
    font-size: 1rem;
    transition: border-color 0.3s ease;
}

.form-group input:focus {
    outline: none;
    border-color: #667eea;
    box-shadow: 0 0 0 3px rgba(102, 126, 234, 0.1);
}

.form-group small {
    display: block;
    margin-top: 5px;
    color: #666;
    font-size: 0.85rem;
}

.form-section {
    margin-top: 30px;
    padding-top: 30px;
    border-top: 1px solid #e0e0e0;
}

.form-section h3 {
    color: #667eea;
    margin-bottom: 10px;
}

.form-help {
    color: #666;
    font-size: 0.9rem;
    margin-bottom: 20px;
}

.btn-full {
    width: 100%;
    padding: 14px;
    font-size: 1.1rem;
}

.auth-footer {
    text-align: center;
    margin-top: 20px;
    padding-top: 20px;
    border-top: 1px solid #e0e0e0;
}

.auth-footer a {
    color: #667eea;
    text-decoration: none;
    font-weight: 500;
}

.auth-footer a:hover {
    text-decoration: underline;
}


/* ==================== Landing Page ====================*/

.landing-container {
    min-height: 100vh;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 40px 20px;
}

.landing-hero {
    text-align: center;
    max-width: 800px;
    margin: 0 auto 80px;
    padding-top: 80px;
}

.landing-hero h1 {
    font-size: 3.5rem;
    margin-bottom: 20px;
}

.landing-subtitle {
    font-size: 1.3rem;
    opacity: 0.95;
    margin-bottom: 40px;
}

.landing-actions {
    display: flex;
    gap: 20px;
    justify-content: center;
}

.btn-large {
    padding: 16px 40px;
    font-size: 1.2rem;
    text-decoration: none;
    display: inline-block;
}

.landing-features {
    max-width: 1000px;
    margin: 0 auto;
}

.landing-features h2 {
    text-align: center;
    font-size: 2.5rem;
    margin-bottom: 40px;
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 30px;
}

.feature-card {
    background: rgba(255,255,255,0.1);
    padding: 30px;
    border-radius: 12px;
    backdrop-filter: blur(10px);
    border: 1px solid rgba(255,255,255,0.2);
}

.feature-card h3 {
    font-size: 1.5rem;
    margin-bottom: 15px;
}

.feature-card p {
    opacity: 0.9;
    line-height: 1.6;
}


/* ==================== Reading Log ====================*/

.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 20px;
    margin-bottom: 30px;
}

.stat-card {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 25px;
    border-radius: 10px;
    text-align: center;
    box-shadow: 0 4px 12px rgba(0,0,0,0.1);
}

.stat-value {
    font-size: 2.5rem;
    font-weight: bold;
    margin-bottom: 5px;
}

.stat-label {
    font-size: 0.95rem;
    opacity: 0.9;
}

.charts-container {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(400px, 1fr));
    gap: 30px;
}

.chart-card {
    background: white;
    padding: 20px;
    border-radius: 10px;
    box-shadow: 0 2px 8px rgba(0,0,0,0.1);
}

.chart-card h3 {
    color: #667eea;
    margin-bottom: 20px;
    text-align: center;
}

.books-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 20px;
}

.book-card {
    background: #f9f9f9;
    padding: 20px;
    border-radius: 8px;
    border: 1px solid #e0e0e0;
    transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.book-card:hover {
    transform: translateY(-4px);
    box-shadow: 0 4px 12px rgba(0,0,0,0.15);
}

.book-cover {
    width: 100%;
    height: 200px;
    object-fit: cover;
    border-radius: 6px;
    margin-bottom: 15px;
}

.book-title {
    font-size: 1.2rem;
    margin-bottom: 5px;
    color: #333;
}

.book-author {
    color: #666;
    font-style: italic;
    margin-bottom: 10px;
}

.book-meta {
    display: flex;
    justify-content: space-between;
    font-size: 0.85rem;
    color: #666;
    margin-bottom: 10px;
}

.book-rating {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-top: 15px;
    padding-top: 15px;
    border-top: 1px solid #e0e0e0;
}

.rating-stars {
    color: #f59e0b;
    font-size: 1.2rem;
}

.btn-small {
    padding: 6px 14px;
    font-size: 0.85rem;
}

.loading {
    text-align: center;
    padding: 40px;
    color: #999;
}


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

@media (max-width: 768px) {
    header h1 {
        font-size: 2rem;
    }

    .actions {
        flex-direction: column;
    }

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

    .history-item {
        flex-direction: column;
        align-items: flex-start;
        gap: 10px;
    }

    .nav-container {
        flex-direction: column;
        gap: 15px;
    }

    .nav-links {
        gap: 15px;
    }

    .landing-hero h1 {
        font-size: 2.5rem;
    }

    .landing-actions {
        flex-direction: column;
        align-items: center;
    }

    .charts-container {
        grid-template-columns: 1fr;
    }

    .stats-grid {
        grid-template-columns: repeat(2, 1fr);
    }
}