:root {
    --primary-color: #2E7D5C;
    --primary-hover: #1B5E3A;
    --primary-light: #4B9B6E;
    --primary-lighter: #6BBF8A;
    --primary-lightest: #A8D5BA;
    --secondary-color: #64748b;
    --success-color: #4B9B6E;
    --warning-color: #f59e0b;
    --error-color: #ef4444;
    --background-primary: #ffffff;
    --background-secondary: #f8fafc;
    --background-tertiary: #f1f5f9;
    --background-accent: #e8f5e9;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --text-muted: #94a3b8;
    --border-color: #e2e8f0;
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
    --radius-sm: 6px;
    --radius-md: 8px;
    --radius-lg: 12px;
}

[data-theme="dark"] {
    --background-primary: #1a1a2e;
    --background-secondary: #16213e;
    --background-tertiary: #0f3460;
    --background-accent: #1a3a2e;
    --text-primary: #e4e4e7;
    --text-secondary: #a1a1aa;
    --text-muted: #71717a;
    --border-color: #3f3f46;
    --primary-color: #4B9B6E;
    --primary-hover: #6BBF8A;
    --primary-light: #6BBF8A;
    --primary-lighter: #A8D5BA;
    --primary-lightest: #2E7D5C;
}

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

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background-color: var(--background-secondary);
    color: var(--text-primary);
    line-height: 1.6;
    min-height: 100vh;
    transition: background-color 0.3s ease, color 0.3s ease;
}

/* Navbar */
.navbar {
    background: var(--background-primary);
    border-bottom: 1px solid var(--border-color);
    padding: 1rem 2rem;
    position: sticky;
    top: 0;
    z-index: 100;
}

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

.nav-brand h1 {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary-color);
}

.nav-tagline {
    font-size: 0.75rem;
    color: var(--text-secondary);
    display: block;
}

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

.nav-link {
    color: var(--text-secondary);
    text-decoration: none;
    font-weight: 500;
    font-size: 0.875rem;
    padding: 0.5rem 0;
    border-bottom: 2px solid transparent;
    transition: all 0.2s ease;
}

.nav-link:hover,
.nav-link.active {
    color: var(--primary-color);
    border-bottom-color: var(--primary-color);
}

.nav-actions {
    display: flex;
    gap: 0.5rem;
}

.icon-btn {
    background: var(--background-tertiary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 0.5rem;
    cursor: pointer;
    color: var(--text-secondary);
    transition: all 0.2s ease;
    display: flex;
    align-items: center;
    justify-content: center;
}

.icon-btn:hover {
    background: var(--primary-lightest);
    color: var(--primary-color);
    border-color: var(--primary-lighter);
}

[data-theme="dark"] .sun-icon {
    display: none !important;
}

[data-theme="dark"] .moon-icon {
    display: block !important;
}

[data-theme="light"] .sun-icon {
    display: block !important;
}

[data-theme="light"] .moon-icon {
    display: none !important;
}

/* Main Content */
.main-content {
    max-width: 1400px;
    margin: 0 auto;
    padding: 2rem;
}

/* Hero Section */
.hero-section {
    text-align: center;
    padding: 3rem 2rem;
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--primary-light) 50%, var(--primary-lighter) 100%);
    border-radius: var(--radius-lg);
    margin-bottom: 2rem;
    color: white;
}

.hero-title {
    font-size: 2rem;
    font-weight: 700;
    margin-bottom: 0.5rem;
}

.hero-subtitle {
    font-size: 1rem;
    opacity: 0.9;
    max-width: 600px;
    margin: 0 auto;
}

/* Cards */
.search-card,
.analysis-card,
.trends-card {
    background: var(--background-primary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 2rem;
    margin-bottom: 2rem;
    box-shadow: var(--shadow-sm);
}

.card-title {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: 1.5rem;
    color: var(--text-primary);
}

/* Form Elements */
.form-grid {
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
    margin-bottom: 1.5rem;
}

.form-row {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 1.5rem;
}

.form-group {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.form-group label {
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--text-primary);
}

.form-group textarea,
.form-group select,
.form-group input {
    padding: 0.75rem 1rem;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    font-size: 0.875rem;
    font-family: inherit;
    background: var(--background-primary);
    color: var(--text-primary);
    transition: border-color 0.2s ease, box-shadow 0.2s ease;
}

.form-group textarea {
    min-height: 100px;
    resize: vertical;
}

.form-group textarea:focus,
.form-group select:focus,
.form-group input:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(46, 125, 92, 0.15);
}

/* Buttons */
.btn-primary,
.btn-secondary,
.btn-small {
    padding: 0.875rem 2rem;
    border: none;
    border-radius: var(--radius-md);
    font-size: 0.875rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s ease;
    font-family: inherit;
}

.btn-primary {
    background: var(--primary-color);
    color: white;
    width: 100%;
}

.btn-primary:hover {
    background: var(--primary-hover);
    transform: translateY(-1px);
}

.btn-primary:disabled {
    background: var(--text-muted);
    cursor: not-allowed;
    transform: none;
}

.btn-secondary {
    background: var(--primary-lightest);
    color: var(--primary-hover);
    border: 1px solid var(--primary-lighter);
}

.btn-secondary:hover {
    background: var(--primary-lighter);
    color: white;
}

.btn-small {
    padding: 0.5rem 1rem;
    font-size: 0.75rem;
    background: var(--background-tertiary);
    color: var(--text-primary);
    border: 1px solid var(--border-color);
}

.btn-small:hover {
    background: var(--primary-lightest);
    border-color: var(--primary-lighter);
}

/* Results Section */
.results-section {
    margin-bottom: 2rem;
}

.results-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1.5rem;
    flex-wrap: wrap;
    gap: 1rem;
}

.results-actions {
    display: flex;
    gap: 0.75rem;
    align-items: center;
}

.section-title {
    font-size: 1.25rem;
    font-weight: 600;
}

.results-stats {
    font-size: 0.875rem;
    color: var(--text-secondary);
}

/* Metrics Grid */
.metrics-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 1rem;
    margin-bottom: 2rem;
}

.metric-card {
    background: var(--background-primary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 1.5rem;
    text-align: center;
    border-left: 4px solid var(--primary-light);
}

.metric-value {
    font-size: 2rem;
    font-weight: 700;
    color: var(--primary-color);
    margin-bottom: 0.25rem;
}

.metric-label {
    font-size: 0.75rem;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

/* Abstracts Container */
.abstracts-container {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.abstract-card {
    background: var(--background-primary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 1.5rem;
    transition: box-shadow 0.2s ease, border-color 0.2s ease;
}

.abstract-card:hover {
    box-shadow: var(--shadow-md);
    border-color: var(--primary-lightest);
}

.abstract-card.selected {
    border-color: var(--primary-color);
    background: var(--background-accent);
}

.abstract-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: 1rem;
    gap: 1rem;
}

.abstract-checkbox {
    flex-shrink: 0;
    width: 20px;
    height: 20px;
    cursor: pointer;
    accent-color: var(--primary-color);
}

.abstract-title {
    font-size: 1rem;
    font-weight: 600;
    color: var(--text-primary);
    flex: 1;
}

.abstract-title a,
.related-item h4 a {
    color: var(--primary-color);
    text-decoration: none;
    transition: color 0.2s ease;
}

.abstract-title a:hover,
.related-item h4 a:hover {
    color: var(--primary-hover);
    text-decoration: underline;
}

.abstract-actions {
    display: flex;
    gap: 0.5rem;
    flex-shrink: 0;
}

.action-btn {
    background: var(--background-tertiary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    padding: 0.25rem 0.5rem;
    font-size: 0.7rem;
    cursor: pointer;
    color: var(--text-secondary);
    transition: all 0.2s ease;
}

.action-btn:hover {
    background: var(--primary-lightest);
    color: var(--primary-color);
    border-color: var(--primary-lighter);
}

.abstract-meta {
    display: flex;
    gap: 1rem;
    flex-wrap: wrap;
    margin-bottom: 1rem;
}

.meta-item {
    font-size: 0.75rem;
    color: var(--text-secondary);
    display: flex;
    align-items: center;
    gap: 0.25rem;
}

.abstract-text {
    font-size: 0.875rem;
    color: var(--text-secondary);
    line-height: 1.7;
}

.abstract-text.collapsed {
    display: -webkit-box;
    -webkit-line-clamp: 3;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

.expand-btn {
    background: none;
    border: none;
    color: var(--primary-color);
    font-size: 0.75rem;
    font-weight: 500;
    cursor: pointer;
    padding: 0.5rem 0;
    margin-top: 0.5rem;
}

.expand-btn:hover {
    text-decoration: underline;
}

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

.empty-icon {
    margin-bottom: 1rem;
    opacity: 0.5;
    color: var(--primary-lighter);
}

.empty-state h4 {
    font-size: 1.125rem;
    margin-bottom: 0.5rem;
    color: var(--text-secondary);
}

.empty-state p {
    font-size: 0.875rem;
}

/* Analysis Section */
.analysis-header,
.trends-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-end;
    margin-bottom: 1.5rem;
    flex-wrap: wrap;
    gap: 1rem;
}

.analysis-controls {
    display: flex;
    align-items: flex-end;
    gap: 1rem;
}

.analysis-controls .form-group {
    min-width: 150px;
}

.analysis-controls .form-group select {
    padding: 0.5rem 0.75rem;
}

.summaries-container {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.summary-card {
    background: linear-gradient(135deg, var(--background-accent) 0%, var(--background-primary) 100%);
    border: 1px solid var(--primary-lightest);
    border-radius: var(--radius-md);
    padding: 1.5rem;
    border-left: 4px solid var(--primary-light);
}

.summary-title {
    font-size: 0.875rem;
    font-weight: 600;
    margin-bottom: 0.75rem;
    color: var(--primary-hover);
}

.summary-text {
    font-size: 0.875rem;
    color: var(--text-secondary);
    line-height: 1.7;
}

/* Trends Section */
.chart-container {
    position: relative;
    height: 300px;
    width: 100%;
}

/* Footer */
.footer {
    background: var(--primary-hover);
    border-top: 1px solid var(--primary-color);
    padding: 2rem;
    text-align: center;
    margin-top: 4rem;
}

.footer-content p {
    font-size: 0.875rem;
    color: rgba(255, 255, 255, 0.9);
}

.footer-note {
    font-size: 0.75rem;
    color: rgba(255, 255, 255, 0.7);
    margin-top: 0.5rem;
}

/* Loading Overlay */
.loading-overlay {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(255, 255, 255, 0.9);
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    z-index: 1000;
}

[data-theme="dark"] .loading-overlay {
    background: rgba(26, 26, 46, 0.9);
}

.loading-spinner {
    width: 48px;
    height: 48px;
    border: 4px solid var(--primary-lightest);
    border-top-color: var(--primary-color);
    border-radius: 50%;
    animation: spin 1s linear infinite;
}

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

.loading-text {
    margin-top: 1rem;
    font-size: 0.875rem;
    color: var(--primary-color);
}

/* Modals */
.modal {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0.5);
    display: flex;
    justify-content: center;
    align-items: center;
    z-index: 2000;
    padding: 2rem;
}

.modal-content {
    background: var(--background-primary);
    border-radius: var(--radius-lg);
    max-width: 500px;
    width: 100%;
    max-height: 80vh;
    overflow: hidden;
    display: flex;
    flex-direction: column;
}

.modal-wide {
    max-width: 900px;
}

.modal-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1.5rem;
    border-bottom: 1px solid var(--border-color);
}

.modal-header h3 {
    font-size: 1.125rem;
    font-weight: 600;
    color: var(--text-primary);
}

.modal-close {
    background: none;
    border: none;
    font-size: 1.5rem;
    cursor: pointer;
    color: var(--text-secondary);
    padding: 0;
    line-height: 1;
}

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

.modal-body {
    padding: 1.5rem;
    overflow-y: auto;
    flex: 1;
}

.modal-footer {
    padding: 1rem 1.5rem;
    border-top: 1px solid var(--border-color);
    display: flex;
    justify-content: flex-end;
    gap: 0.75rem;
}

/* History List */
.history-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0.75rem;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    margin-bottom: 0.5rem;
    cursor: pointer;
    transition: all 0.2s ease;
}

.history-item:hover {
    background: var(--background-tertiary);
    border-color: var(--primary-lighter);
}

.history-query {
    font-weight: 500;
    color: var(--text-primary);
    flex: 1;
}

.history-date {
    font-size: 0.75rem;
    color: var(--text-muted);
}

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

/* Compare Grid */
.compare-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 1rem;
}

.compare-item {
    background: var(--background-tertiary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 1rem;
}

.compare-item h4 {
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 0.5rem;
}

.compare-item p {
    font-size: 0.8rem;
    color: var(--text-secondary);
    line-height: 1.6;
}

/* Citation Output */
.citation-output {
    background: var(--background-tertiary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 1rem;
    margin: 1rem 0;
    font-size: 0.875rem;
    color: var(--text-primary);
    line-height: 1.6;
    min-height: 80px;
}

/* Related Papers */
.related-item {
    background: var(--background-tertiary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 1rem;
    margin-bottom: 0.75rem;
}

.related-item h4 {
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--primary-color);
    margin-bottom: 0.5rem;
}

.related-item p {
    font-size: 0.8rem;
    color: var(--text-secondary);
}

/* Responsive */
@media (max-width: 768px) {
    .nav-links {
        display: none;
    }
    
    .form-row {
        grid-template-columns: 1fr;
    }
    
    .metrics-grid {
        grid-template-columns: repeat(2, 1fr);
    }
    
    .hero-title {
        font-size: 1.5rem;
    }
    
    .main-content {
        padding: 1rem;
    }
    
    .analysis-header,
    .trends-header {
        flex-direction: column;
        align-items: stretch;
    }
    
    .analysis-controls {
        flex-direction: column;
    }
    
    .compare-grid {
        grid-template-columns: 1fr;
    }
    
    .results-header {
        flex-direction: column;
        align-items: flex-start;
    }
    
    .results-actions {
        width: 100%;
        justify-content: space-between;
    }
}

@media (max-width: 480px) {
    .metrics-grid {
        grid-template-columns: 1fr;
    }
    
    .modal-content {
        margin: 1rem;
    }
}