:root {
    --primary-color: #6366f1;
    --primary-light: #818cf8;
    --primary-dark: #4f46e5;
    --secondary-color: #10b981;
    --accent-color: #f59e0b;
    --background-color: #0f172a;
    --card-background: #1e293b;
    --surface-light: rgba(30, 41, 59, 0.7);
    --surface-dark: rgba(15, 23, 42, 0.7);
    --text-primary: rgba(255, 255, 255, 0.95);
    --text-secondary: rgba(255, 255, 255, 0.7);
    --border-color: rgba(255, 255, 255, 0.08);
    --error-color: #ef4444;
    --success-color: #10b981;
    --shadow-color: rgba(0, 0, 0, 0.25);
}

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

body {
    background: var(--background-color);
    color: var(--text-primary);
    font-family: 'Space Grotesk', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    min-height: 100vh;
    line-height: 1.6;
    font-size: 16px;
}

/* Layout */
.app-container {
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    max-width: 1440px;
    margin: 0 auto;
    padding: 0 1rem;
}

/* Navigation */
.top-nav {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1.25rem 0;
    border-bottom: 1px solid var(--border-color);
    margin-bottom: 1.5rem;
}

.nav-left {
    display: flex;
    align-items: center;
}

.logo {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary-light);
    margin: 0;
    background: linear-gradient(135deg, var(--primary-light), var(--secondary-color));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    letter-spacing: -0.5px;
}

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

.user-info {
    font-size: 0.9rem;
    color: var(--text-secondary);
}

.logout-button {
    background: rgba(99, 102, 241, 0.1);
    color: var(--primary-light);
    text-decoration: none;
    padding: 0.5rem 1rem;
    border-radius: 0.5rem;
    font-size: 0.875rem;
    font-weight: 500;
    transition: all 0.2s ease;
    border: 1px solid rgba(99, 102, 241, 0.2);
}

.logout-button:hover {
    background: rgba(99, 102, 241, 0.2);
    transform: translateY(-1px);
}

/* Breadcrumb */
.breadcrumb {
    display: flex;
    align-items: center;
    gap: 1rem;
    margin-bottom: 1.5rem;
    font-size: 0.9rem;
}

#currentSection {
    font-weight: 600;
    color: var(--text-primary);
}

.back-button {
    background: transparent;
    border: none;
    color: var(--primary-light);
    cursor: pointer;
    font-size: 0.9rem;
    display: flex;
    align-items: center;
    gap: 0.25rem;
    padding: 0.25rem 0.5rem;
    border-radius: 0.25rem;
    transition: all 0.2s ease;
}

.back-button:hover {
    background: rgba(99, 102, 241, 0.1);
}

/* Main Content */
.main-content {
    flex: 1;
    display: flex;
    flex-direction: column;
}

.content-section {
    display: none;
}

.content-section.active {
    display: block;
    animation: fadeIn 0.3s ease;
}

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

/* Search Section */
.search-section {
    display: flex;
    flex-direction: column;
    gap: 2rem;
    margin-bottom: 2rem;
}

.search-container {
    display: flex;
    flex-wrap: wrap;
    gap: 1rem;
    align-items: center;
    background: var(--card-background);
    padding: 1.5rem;
    border-radius: 1rem;
    box-shadow: 0 4px 20px var(--shadow-color);
}

.search-input {
    flex: 1;
    min-width: 250px;
    background: rgba(15, 23, 42, 0.5);
    border: 1px solid var(--border-color);
    border-radius: 0.5rem;
    padding: 0.875rem 1.25rem;
    font-size: 1rem;
    color: var(--text-primary);
    transition: all 0.2s ease;
}

.search-input:focus {
    outline: none;
    border-color: var(--primary-light);
    box-shadow: 0 0 0 2px rgba(99, 102, 241, 0.2);
}

.search-input::placeholder {
    color: var(--text-secondary);
    opacity: 0.7;
}

.filter-select {
    background: rgba(15, 23, 42, 0.5);
    border: 1px solid var(--border-color);
    border-radius: 0.5rem;
    color: var(--text-primary);
    padding: 0.875rem 2.5rem 0.875rem 1.25rem;
    font-size: 0.9rem;
    cursor: pointer;
    outline: none;
    min-width: 140px;
    appearance: none;
    background-image: url("data:image/svg+xml;charset=UTF-8,%3csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='white' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3e%3cpolyline points='6 9 12 15 18 9'%3e%3c/polyline%3e%3c/svg%3e");
    background-repeat: no-repeat;
    background-position: right 1rem center;
    background-size: 1em;
    transition: all 0.2s ease;
}

.filter-select:hover, .filter-select:focus {
    border-color: var(--primary-light);
}

.search-button {
    background: linear-gradient(135deg, var(--primary-color), var(--primary-dark));
    color: white;
    border: none;
    padding: 0.875rem 1.5rem;
    border-radius: 0.5rem;
    font-size: 0.9rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s ease;
    text-transform: uppercase;
    letter-spacing: 1px;
    min-width: 120px;
    box-shadow: 0 4px 12px rgba(79, 70, 229, 0.2);
}

.search-button:hover {
    transform: translateY(-1px);
    box-shadow: 0 6px 16px rgba(79, 70, 229, 0.3);
}

.search-button:active {
    transform: translateY(0);
    box-shadow: 0 2px 8px rgba(79, 70, 229, 0.2);
}

/* Feature Cards */
.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 1.5rem;
    margin-top: 1rem;
}

.feature-card {
    background: var(--card-background);
    border-radius: 1rem;
    padding: 1.5rem;
    display: flex;
    align-items: flex-start;
    gap: 1rem;
    transition: all 0.3s ease;
    border: 1px solid var(--border-color);
    margin-bottom: 1rem;
}

.feature-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 25px rgba(0, 0, 0, 0.1);
    border-color: var(--primary-light);
}

.feature-icon {
    font-size: 1.75rem;
    background: linear-gradient(135deg, var(--primary-light), var(--secondary-color));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.feature-content {
    flex: 1;
}

.feature-title {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: 0.5rem;
    color: var(--text-primary);
}

.feature-description {
    font-size: 0.9rem;
    color: var(--text-secondary);
    line-height: 1.5;
}

/* Results Section */
.results-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 1.5rem;
    margin-top: 1.5rem;
}

.paper-card {
    background: var(--card-background);
    border-radius: 1rem;
    padding: 1.5rem;
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
    transition: all 0.3s ease;
    border: 1px solid var(--border-color);
    height: 100%;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
}

.paper-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 25px rgba(0, 0, 0, 0.15);
    border-color: var(--primary-light);
}

.paper-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 0.25rem;
}

.paper-title {
    font-size: 1.25rem;
    font-weight: 600;
    line-height: 1.4;
    color: var(--text-primary);
    margin-bottom: 0.5rem;
}

.paper-authors {
    font-size: 0.9rem;
    color: var(--text-secondary);
    margin-bottom: 0.5rem;
}

.paper-abstract {
    font-size: 0.9rem;
    line-height: 1.6;
    color: var(--text-secondary);
    flex-grow: 1;
}

.paper-actions {
    display: flex;
    gap: 0.75rem;
    margin-top: 1rem;
}

.paper-button {
    padding: 0.75rem 1rem;
    border-radius: 0.5rem;
    font-size: 0.85rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s ease;
    text-align: center;
    text-decoration: none;
    flex: 1;
    border: none;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}

.pdf-button {
    background: rgba(30, 41, 59, 0.8);
    color: #e2e8f0;
}

.pdf-button:hover {
    background: rgba(44, 55, 74, 0.9);
    transform: translateY(-2px);
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.25);
}

.arxiv-button {
    background: rgba(99, 102, 241, 0.2);
    color: #e2e8f0;
}

.arxiv-button:hover {
    background: rgba(99, 102, 241, 0.3);
    transform: translateY(-2px);
    box-shadow: 0 4px 8px rgba(99, 102, 241, 0.25);
}

.analyze-button {
    background: linear-gradient(135deg, var(--primary-color), var(--primary-dark));
    color: white;
}

.analyze-button:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 8px rgba(99, 102, 241, 0.4);
    background: linear-gradient(135deg, var(--primary-light), var(--primary-color));
}

/* Loading Overlay */
.loading-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(15, 23, 42, 0.9);
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    z-index: 1000;
    backdrop-filter: blur(5px);
}

.loading-overlay.hidden {
    display: none;
}

.loading-spinner {
    width: 50px;
    height: 50px;
    border: 3px solid rgba(255, 255, 255, 0.1);
    border-radius: 50%;
    border-top-color: var(--primary-light);
    animation: spin 1s linear infinite;
    margin-bottom: 1rem;
}

.loading-overlay p {
    color: var(--text-primary);
    font-size: 1rem;
    font-weight: 500;
}

@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}

/* Chat Interface */
.chat-container {
    height: 500px;
    display: flex;
    flex-direction: column;
    background: var(--card-background);
    border-radius: 1rem;
    overflow: hidden;
    border: 1px solid var(--border-color);
    box-shadow: 0 4px 20px var(--shadow-color);
}

.quick-questions {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    padding: 1rem;
    background: rgba(15, 23, 42, 0.5);
    border-bottom: 1px solid var(--border-color);
}

.quick-question-btn {
    background: rgba(99, 102, 241, 0.1);
    border: 1px solid rgba(99, 102, 241, 0.2);
    color: var(--primary-light);
    padding: 0.5rem 1rem;
    border-radius: 2rem;
    font-size: 0.8rem;
    cursor: pointer;
    transition: all 0.2s ease;
    white-space: nowrap;
}

.quick-question-btn:hover {
    background: rgba(99, 102, 241, 0.2);
}

.chat-messages {
    flex: 1;
    overflow-y: auto;
    padding: 1.5rem;
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.message-wrapper {
    display: flex;
    gap: 0.75rem;
    max-width: 85%;
}

.message-avatar {
    width: 2rem;
    height: 2rem;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.8rem;
    font-weight: 600;
    flex-shrink: 0;
}

.ai-avatar {
    background: linear-gradient(135deg, var(--primary-color), var(--primary-dark));
    color: white;
}

.user-avatar {
    background: linear-gradient(135deg, var(--secondary-color), #059669);
    color: white;
}

.message {
    padding: 1rem;
    border-radius: 0.75rem;
    font-size: 0.9rem;
    line-height: 1.6;
}

.ai-message {
    background: rgba(15, 23, 42, 0.5);
    color: var(--text-primary);
    border-bottom-left-radius: 0.25rem;
    align-self: flex-start;
}

.user-message {
    background: rgba(99, 102, 241, 0.1);
    color: var(--text-primary);
    border-bottom-right-radius: 0.25rem;
    align-self: flex-end;
}

.chat-input-area {
    display: flex;
    gap: 0.75rem;
    padding: 1rem;
    background: rgba(15, 23, 42, 0.5);
    border-top: 1px solid var(--border-color);
}

.chat-input {
    flex: 1;
    background: rgba(15, 23, 42, 0.5);
    border: 1px solid var(--border-color);
    border-radius: 0.5rem;
    padding: 0.75rem 1rem;
    color: var(--text-primary);
    font-size: 0.9rem;
}

.chat-input:focus {
    outline: none;
    border-color: var(--primary-light);
}

.chat-send-button {
    background: linear-gradient(135deg, var(--primary-color), var(--primary-dark));
    color: white;
    border: none;
    border-radius: 0.5rem;
    padding: 0.75rem 1rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
    cursor: pointer;
    transition: all 0.2s ease;
}

.chat-send-button:hover {
    transform: translateY(-1px);
    box-shadow: 0 4px 12px rgba(79, 70, 229, 0.2);
}

.ai-thinking {
    display: flex;
    align-items: center;
    padding: 0.75rem 1rem;
    background: rgba(15, 23, 42, 0.3);
    border-radius: 0.75rem;
    min-width: 80px;
}

.ai-thinking-dots {
    display: flex;
    gap: 4px;
    justify-content: center;
    align-items: center;
    height: 24px;
}

.ai-thinking-dot {
    width: 6px;
    height: 6px;
    background: var(--primary-light);
    border-radius: 50%;
    animation: thinking 1.4s infinite ease-in-out;
}

.ai-thinking-dot:nth-child(1) {
    animation-delay: 0s;
}

.ai-thinking-dot:nth-child(2) {
    animation-delay: 0.2s;
}

.ai-thinking-dot:nth-child(3) {
    animation-delay: 0.4s;
}

@keyframes thinking {
    0%, 60%, 100% { 
        transform: scale(0.6);
        opacity: 0.3;
    }
    30% { 
        transform: scale(1);
        opacity: 1;
    }
}

/* Analysis Styles */
.analysis-container {
    background: var(--card-background);
    border-radius: 1rem;
    padding: 2rem;
    margin-top: 1.5rem;
    border: 1px solid var(--border-color);
    box-shadow: 0 4px 20px var(--shadow-color);
}

.analysis-header {
    margin-bottom: 2rem;
    padding-bottom: 1rem;
    border-bottom: 1px solid var(--border-color);
    text-align: center;
}

.analysis-header h2 {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary-light);
    margin-bottom: 0.5rem;
}

.analysis-section {
    margin-bottom: 1.5rem;
    padding: 1.5rem;
    background: rgba(15, 23, 42, 0.3);
    border-radius: 0.75rem;
    border: 1px solid var(--border-color);
    transition: all 0.3s ease;
}

.analysis-section:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 15px var(--shadow-color);
    border-color: var(--primary-light);
}

.analysis-section h3 {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: 1rem;
    color: var(--text-primary);
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.analysis-section p {
    font-size: 0.95rem;
    line-height: 1.7;
    color: var(--text-secondary);
}

/* History Section */
.history-grid, .saved-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 1.5rem;
}

.history-card {
    background: var(--card-background);
    border-radius: 1rem;
    padding: 1.5rem;
    border: 1px solid var(--border-color);
    transition: all 0.3s ease;
}

.history-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 25px rgba(0, 0, 0, 0.1);
    border-color: var(--primary-light);
}

.history-card h3 {
    font-size: 1.1rem;
    font-weight: 600;
    margin-bottom: 0.5rem;
    color: var(--text-primary);
}

.timestamp {
    font-size: 0.8rem;
    color: var(--text-secondary);
    margin-bottom: 1rem;
}

/* Notifications */
.notification {
    position: fixed;
    bottom: 2rem;
    right: 2rem;
    padding: 1rem 1.5rem;
    border-radius: 0.5rem;
    background: var(--card-background);
    color: var(--text-primary);
    font-size: 0.9rem;
    box-shadow: 0 4px 20px var(--shadow-color);
    transform: translateY(100px);
    opacity: 0;
    transition: all 0.3s ease;
    z-index: 1000;
    max-width: 300px;
}

.notification.show {
    transform: translateY(0);
    opacity: 1;
}

.notification.info {
    border-left: 4px solid var(--primary-color);
}

.notification.success {
    border-left: 4px solid var(--success-color);
}

.notification.error {
    border-left: 4px solid var(--error-color);
}

/* Responsive Design */
@media (max-width: 768px) {
    .app-container {
        padding: 0 0.75rem;
    }
    
    .top-nav {
        padding: 1rem 0;
    }
    
    .logo {
        font-size: 1.25rem;
    }
    
    .search-container {
        padding: 1rem;
        flex-direction: column;
        align-items: stretch;
    }
    
    .search-input, .filter-select, .search-button {
        width: 100%;
    }
    
    .results-grid, .history-grid, .saved-grid, .features-grid {
        grid-template-columns: 1fr;
    }
    
    .paper-card, .history-card {
        padding: 1.25rem;
    }
    
    .paper-title {
        font-size: 1.1rem;
    }
    
    .action-row {
        flex-direction: column;
    }
    
    .chat-container {
        height: 400px;
    }
    
    .quick-questions {
        overflow-x: auto;
        padding: 0.75rem;
        justify-content: flex-start;
    }
    
    .message-wrapper {
        max-width: 95%;
    }
    
    .analysis-container {
        padding: 1.25rem;
    }
    
    .paper-actions {
        flex-direction: column;
    }
    
    .paper-button {
        width: 100%;
    }
}

@media (min-width: 769px) and (max-width: 1024px) {
    .results-grid, .history-grid, .saved-grid, .features-grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

/* Dark mode scrollbar */
::-webkit-scrollbar {
    width: 8px;
    height: 8px;
}

::-webkit-scrollbar-track {
    background: rgba(15, 23, 42, 0.5);
}

::-webkit-scrollbar-thumb {
    background: rgba(99, 102, 241, 0.5);
    border-radius: 4px;
}

::-webkit-scrollbar-thumb:hover {
    background: rgba(99, 102, 241, 0.7);
}

/* Direct PDF Input Section */
.direct-pdf-section {
    margin-top: 1.5rem;
}

.direct-pdf-container {
    background: var(--card-background);
    padding: 1.5rem;
    border-radius: 1rem;
    box-shadow: 0 4px 20px var(--shadow-color);
    border: 1px solid var(--border-color);
}

.direct-pdf-container h3 {
    color: var(--primary-light);
    font-size: 1.25rem;
    margin-bottom: 0.5rem;
}

.direct-pdf-description {
    color: var(--text-secondary);
    font-size: 0.9rem;
    margin-bottom: 1rem;
}

.direct-pdf-input-container {
    display: flex;
    gap: 1rem;
    flex-wrap: wrap;
}

.direct-pdf-input-container .search-input {
    flex: 1;
    min-width: 250px;
}

.direct-pdf-input-container .search-button {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

/* Responsive adjustments */
@media (max-width: 768px) {
    .direct-pdf-input-container {
        flex-direction: column;
    }
    
    .direct-pdf-input-container .search-button {
        width: 100%;
        justify-content: center;
    }
}