/* Reset and Base Styles */
* {
    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: #1f2937;
    background-color: #f8fafc;
}

/* Color System */
:root {
    --primary: #1e3a8a;
    --primary-light: #3b82f6;
    --primary-dark: #1e40af;
    --secondary: #059669;
    --accent: #d97706;
    --success: #10b981;
    --warning: #f59e0b;
    --error: #ef4444;
    --neutral-50: #f8fafc;
    --neutral-100: #f1f5f9;
    --neutral-200: #e2e8f0;
    --neutral-300: #cbd5e1;
    --neutral-400: #94a3b8;
    --neutral-500: #64748b;
    --neutral-600: #475569;
    --neutral-700: #334155;
    --neutral-800: #1e293b;
    --neutral-900: #0f172a;
    --spacing: 8px;
}

/* Navigation */
.navbar {
    background: linear-gradient(135deg, var(--primary) 0%, var(--primary-dark) 100%);
    color: white;
    padding: calc(var(--spacing) * 2) 0;
    box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    position: sticky;
    top: 0;
    z-index: 100;
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0 calc(var(--spacing) * 3);
}

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

.university-logo {
    display: flex;
    align-items: center;
    gap: calc(var(--spacing) * 2);
}

.logo-svg {
    width: 40px;
    height: 40px;
    transition: transform 0.3s ease;
}

.logo-svg:hover {
    transform: scale(1.1);
}

.university-name {
    font-size: 20px;
    font-weight: 600;
}

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

.course-code {
    display: block;
    font-size: 18px;
    font-weight: 700;
    color: var(--accent);
}

.course-name {
    display: block;
    font-size: 14px;
    opacity: 0.9;
}

.user-profile {
    display: flex;
    align-items: center;
    gap: calc(var(--spacing) * 2);
}

.user-avatar {
    width: 32px;
    height: 32px;
    background: var(--accent);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: bold;
    font-size: 14px;
}

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

/* Main Content */
.main-content {
    max-width: 1200px;
    margin: 0 auto;
    padding: calc(var(--spacing) * 4) calc(var(--spacing) * 3);
}

/* Forum Header */
.forum-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-end;
    margin-bottom: calc(var(--spacing) * 4);
    padding-bottom: calc(var(--spacing) * 3);
    border-bottom: 2px solid var(--neutral-200);
}

.forum-title h1 {
    font-size: 28px;
    font-weight: 700;
    color: var(--neutral-900);
    margin-bottom: calc(var(--spacing) * 1);
    line-height: 1.2;
}

.forum-title p {
    color: var(--neutral-600);
    font-size: 16px;
}

/* Buttons */
.btn-primary, .btn-secondary {
    padding: calc(var(--spacing) * 2) calc(var(--spacing) * 3);
    border: none;
    border-radius: calc(var(--spacing) * 1);
    font-weight: 600;
    font-size: 14px;
    cursor: pointer;
    transition: all 0.3s ease;
    display: inline-flex;
    align-items: center;
    gap: calc(var(--spacing) * 1);
    text-decoration: none;
}

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

.btn-primary:hover {
    background: var(--primary-dark);
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(30, 58, 138, 0.4);
}

.btn-secondary {
    background: var(--neutral-200);
    color: var(--neutral-700);
}

.btn-secondary:hover {
    background: var(--neutral-300);
    transform: translateY(-1px);
}

.btn-icon {
    font-size: 16px;
    font-weight: bold;
}

/* Forum Controls */
.forum-controls {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: calc(var(--spacing) * 4);
    gap: calc(var(--spacing) * 3);
}

.search-container {
    display: flex;
    gap: calc(var(--spacing) * 2);
    flex: 1;
    max-width: 400px;
}

.search-input {
    flex: 1;
    padding: calc(var(--spacing) * 2);
    border: 2px solid var(--neutral-300);
    border-radius: calc(var(--spacing) * 1);
    font-size: 14px;
    transition: all 0.3s ease;
}

.search-input:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(30, 58, 138, 0.1);
}

.search-btn {
    padding: calc(var(--spacing) * 2) calc(var(--spacing) * 3);
    background: var(--primary);
    color: white;
    border: none;
    border-radius: calc(var(--spacing) * 1);
    cursor: pointer;
    font-weight: 600;
    transition: all 0.3s ease;
}

.search-btn:hover {
    background: var(--primary-dark);
}

.filter-controls {
    display: flex;
    gap: calc(var(--spacing) * 2);
}

.filter-select {
    padding: calc(var(--spacing) * 2);
    border: 2px solid var(--neutral-300);
    border-radius: calc(var(--spacing) * 1);
    background: white;
    font-size: 14px;
    cursor: pointer;
    transition: all 0.3s ease;
}

.filter-select:focus {
    outline: none;
    border-color: var(--primary);
}

/* Thread List */
.thread-list {
    display: flex;
    flex-direction: column;
    gap: calc(var(--spacing) * 3);
}

.thread-card {
    background: white;
    border-radius: calc(var(--spacing) * 2);
    padding: calc(var(--spacing) * 3);
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
    border: 1px solid var(--neutral-200);
    transition: all 0.3s ease;
    cursor: pointer;
}

.thread-card:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
    border-color: var(--primary-light);
}

.thread-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: calc(var(--spacing) * 2);
}

.thread-title {
    font-size: 18px;
    font-weight: 600;
    color: var(--neutral-900);
    margin-bottom: calc(var(--spacing) * 1);
    line-height: 1.4;
}

.thread-meta {
    display: flex;
    align-items: center;
    gap: calc(var(--spacing) * 2);
    font-size: 12px;
    color: var(--neutral-500);
}

.thread-status {
    padding: calc(var(--spacing) * 0.5) calc(var(--spacing) * 2);
    border-radius: calc(var(--spacing) * 3);
    font-size: 11px;
    font-weight: 600;
    text-transform: uppercase;
}

.status-answered {
    background: rgba(16, 185, 129, 0.1);
    color: var(--success);
}

.status-unanswered {
    background: rgba(239, 68, 68, 0.1);
    color: var(--error);
}

.thread-preview {
    color: var(--neutral-600);
    font-size: 14px;
    line-height: 1.5;
    margin-bottom: calc(var(--spacing) * 2);
}

.thread-footer {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.thread-votes {
    display: flex;
    align-items: center;
    gap: calc(var(--spacing) * 2);
}

.vote-btn {
    background: none;
    border: 1px solid var(--neutral-300);
    padding: calc(var(--spacing) * 1);
    border-radius: calc(var(--spacing) * 1);
    cursor: pointer;
    transition: all 0.3s ease;
    display: flex;
    align-items: center;
    justify-content: center;
    width: 32px;
    height: 32px;
}

.vote-btn:hover {
    background: var(--neutral-100);
}

.vote-btn.voted {
    background: var(--primary);
    color: white;
    border-color: var(--primary);
}

.vote-count {
    font-weight: 600;
    color: var(--neutral-700);
    min-width: 30px;
    text-align: center;
}

.thread-actions {
    display: flex;
    gap: calc(var(--spacing) * 2);
}

.action-btn {
    background: none;
    border: none;
    color: var(--primary);
    font-size: 12px;
    font-weight: 500;
    cursor: pointer;
    padding: calc(var(--spacing) * 1);
    border-radius: calc(var(--spacing) * 1);
    transition: all 0.3s ease;
}

.action-btn:hover {
    background: rgba(30, 58, 138, 0.1);
}

/* Thread Detail */
.thread-detail {
    animation: slideIn 0.3s ease;
}

@keyframes slideIn {
    from {
        opacity: 0;
        transform: translateX(20px);
    }
    to {
        opacity: 1;
        transform: translateX(0);
    }
}

.thread-detail-header {
    margin-bottom: calc(var(--spacing) * 3);
}

.question-section, .answer-section {
    background: white;
    border-radius: calc(var(--spacing) * 2);
    padding: calc(var(--spacing) * 4);
    margin-bottom: calc(var(--spacing) * 3);
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
    border: 1px solid var(--neutral-200);
}

.section-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: calc(var(--spacing) * 3);
    padding-bottom: calc(var(--spacing) * 2);
    border-bottom: 1px solid var(--neutral-200);
}

.section-title {
    font-size: 16px;
    font-weight: 600;
    color: var(--neutral-800);
}

.ai-badge {
    background: linear-gradient(135deg, var(--secondary) 0%, #10b981 100%);
    color: white;
    padding: calc(var(--spacing) * 1) calc(var(--spacing) * 2);
    border-radius: calc(var(--spacing) * 3);
    font-size: 11px;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

/* Retry button specific styles */
.section-header .btn-secondary {
    font-size: 13px;
    padding: calc(var(--spacing) * 1) calc(var(--spacing) * 2);
    min-width: auto;
}

.section-header .btn-icon {
    font-size: 12px;
    margin-right: calc(var(--spacing) * 0.5);
}

.content-body {
    font-size: 15px;
    line-height: 1.7;
    color: var(--neutral-700);
}

.content-body h1, .content-body h2, .content-body h3 {
    color: var(--neutral-900);
    margin: calc(var(--spacing) * 3) 0 calc(var(--spacing) * 2) 0;
    font-weight: 600;
}

.content-body h1 { font-size: 24px; }
.content-body h2 { font-size: 20px; }
.content-body h3 { font-size: 18px; }

.content-body p {
    margin-bottom: calc(var(--spacing) * 2);
}

.content-body ul, .content-body ol {
    margin: calc(var(--spacing) * 2) 0;
    padding-left: calc(var(--spacing) * 4);
}

.content-body li {
    margin-bottom: calc(var(--spacing) * 1);
}

.content-body code {
    background: var(--neutral-100);
    padding: calc(var(--spacing) * 0.5) calc(var(--spacing) * 1);
    border-radius: calc(var(--spacing) * 0.5);
    font-family: 'Monaco', 'Menlo', 'Ubuntu Mono', monospace;
    font-size: 13px;
}

.content-body pre {
    background: var(--neutral-100);
    padding: calc(var(--spacing) * 2);
    border-radius: calc(var(--spacing) * 1);
    overflow-x: auto;
    margin: calc(var(--spacing) * 2) 0;
}

.content-body blockquote {
    border-left: 4px solid var(--primary);
    padding-left: calc(var(--spacing) * 2);
    margin: calc(var(--spacing) * 2) 0;
    font-style: italic;
    color: var(--neutral-600);
}

/* Replies Section */
.replies-section {
    margin-top: calc(var(--spacing) * 4);
}

.replies-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: calc(var(--spacing) * 3);
}

.replies-title {
    font-size: 18px;
    font-weight: 600;
    color: var(--neutral-900);
}

.reply-card {
    background: white;
    border-radius: calc(var(--spacing) * 2);
    padding: calc(var(--spacing) * 3);
    margin-bottom: calc(var(--spacing) * 2);
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
    border: 1px solid var(--neutral-200);
    border-left: 4px solid var(--primary-light);
}

.reply-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: calc(var(--spacing) * 2);
}

.reply-author {
    font-weight: 600;
    color: var(--neutral-800);
}

.reply-date {
    font-size: 12px;
    color: var(--neutral-500);
}

.reply-content {
    color: var(--neutral-700);
    line-height: 1.6;
}

/* Modal */
.modal-overlay {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0.5);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 1000;
    padding: calc(var(--spacing) * 2);
}

.modal {
    background: white;
    border-radius: calc(var(--spacing) * 2);
    width: 100%;
    max-width: 600px;
    max-height: 90vh;
    overflow-y: auto;
    box-shadow: 0 20px 25px -5px rgba(0, 0, 0, 0.1);
    animation: modalSlideIn 0.3s ease;
}

@keyframes modalSlideIn {
    from {
        opacity: 0;
        transform: scale(0.9) translateY(-20px);
    }
    to {
        opacity: 1;
        transform: scale(1) translateY(0);
    }
}

.modal-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: calc(var(--spacing) * 3);
    border-bottom: 1px solid var(--neutral-200);
}

.modal-header h2 {
    font-size: 20px;
    font-weight: 600;
    color: var(--neutral-900);
}

.modal-close {
    background: none;
    border: none;
    font-size: 24px;
    color: var(--neutral-400);
    cursor: pointer;
    padding: calc(var(--spacing) * 1);
    border-radius: calc(var(--spacing) * 1);
    transition: all 0.3s ease;
}

.modal-close:hover {
    background: var(--neutral-100);
    color: var(--neutral-600);
}

.modal-body {
    padding: calc(var(--spacing) * 3);
}

/* Form Styles */
.form-group {
    margin-bottom: calc(var(--spacing) * 3);
}

.form-group label {
    display: block;
    font-weight: 600;
    color: var(--neutral-700);
    margin-bottom: calc(var(--spacing) * 1);
    font-size: 14px;
}

.form-group input, .form-group textarea {
    width: 100%;
    padding: calc(var(--spacing) * 2);
    border: 2px solid var(--neutral-300);
    border-radius: calc(var(--spacing) * 1);
    font-size: 14px;
    font-family: inherit;
    transition: all 0.3s ease;
    resize: vertical;
}

.form-group input:focus, .form-group textarea:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(30, 58, 138, 0.1);
}

.form-actions {
    display: flex;
    justify-content: flex-end;
    gap: calc(var(--spacing) * 2);
    margin-top: calc(var(--spacing) * 4);
}

/* Loading States */
.loading-overlay {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(255, 255, 255, 0.9);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 2000;
}

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

.spinner {
    width: 40px;
    height: 40px;
    border: 3px solid var(--neutral-200);
    border-top: 3px solid var(--primary);
    border-radius: 50%;
    animation: spin 1s linear infinite;
    margin: 0 auto calc(var(--spacing) * 2) auto;
}

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

.loading-spinner p {
    color: var(--neutral-600);
    font-weight: 500;
}

/* Empty State */
.empty-state {
    text-align: center;
    padding: calc(var(--spacing) * 8) calc(var(--spacing) * 3);
    color: var(--neutral-500);
}

.empty-state h3 {
    font-size: 18px;
    font-weight: 600;
    margin-bottom: calc(var(--spacing) * 1);
    color: var(--neutral-700);
}

/* Math Formulas */
.MathJax {
    font-size: 1.1em !important;
}

/* Responsive Design */
@media (max-width: 1024px) {
    .nav-container {
        padding: 0 calc(var(--spacing) * 2);
    }
    
    .main-content {
        padding: calc(var(--spacing) * 3) calc(var(--spacing) * 2);
    }
    
    .forum-header {
        flex-direction: column;
        align-items: flex-start;
        gap: calc(var(--spacing) * 2);
    }
    
    .forum-controls {
        flex-direction: column;
        align-items: stretch;
    }
    
    .search-container {
        max-width: none;
    }
    
    .filter-controls {
        justify-content: space-between;
    }
}

@media (max-width: 768px) {
    .nav-container {
        flex-direction: column;
        gap: calc(var(--spacing) * 2);
        text-align: center;
    }
    
    .nav-course {
        order: -1;
    }
    
    .university-logo {
        justify-content: center;
    }
    
    .forum-title h1 {
        font-size: 24px;
    }
    
    .thread-card {
        padding: calc(var(--spacing) * 2);
    }
    
    .thread-header {
        flex-direction: column;
        align-items: flex-start;
        gap: calc(var(--spacing) * 1);
    }
    
    .thread-footer {
        flex-direction: column;
        align-items: flex-start;
        gap: calc(var(--spacing) * 2);
    }
    
    .modal {
        margin: calc(var(--spacing) * 2);
        max-height: calc(100vh - var(--spacing) * 4);
    }
    
    .form-actions {
        flex-direction: column;
    }
    
    .form-actions button {
        width: 100%;
    }
    
    /* Mobile styles for section headers */
    .section-header {
        flex-direction: column;
        align-items: flex-start;
        gap: calc(var(--spacing) * 2);
    }
    
    .section-header .btn-secondary {
        align-self: flex-end;
        font-size: 12px;
        padding: calc(var(--spacing) * 0.75) calc(var(--spacing) * 1.5);
    }
}

/* Utility Classes */
.text-center { text-align: center; }
.text-success { color: var(--success); }
.text-error { color: var(--error); }
.text-warning { color: var(--warning); }

.bg-success-light { background: rgba(16, 185, 129, 0.1); }
.bg-error-light { background: rgba(239, 68, 68, 0.1); }
.bg-warning-light { background: rgba(245, 158, 11, 0.1); }

.fade-in {
    animation: fadeIn 0.5s ease;
}

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

/* Accessibility */
@media (prefers-reduced-motion: reduce) {
    *, *::before, *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
}

/* Focus styles for accessibility */
button:focus-visible, input:focus-visible, textarea:focus-visible, select:focus-visible {
    outline: 2px solid var(--primary);
    outline-offset: 2px;
}

/* Footer */
.footer {
    background: var(--neutral-100);
    border-top: 1px solid var(--neutral-200);
    padding: calc(var(--spacing) * 3) 0;
    margin-top: calc(var(--spacing) * 8);
}

.footer-content {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 calc(var(--spacing) * 3);
    text-align: center;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.footer-info {
    display: flex;
    justify-content: center;
    align-items: center;
    gap: calc(var(--spacing) * 2);
    font-size: 14px;
    color: var(--neutral-600);
}

.footer-info a {
    color: var(--primary);
    text-decoration: none;
    transition: color 0.3s ease;
}

.footer-info a:hover {
    color: var(--primary-dark);
    text-decoration: underline;
}

.footer-separator {
    color: var(--neutral-400);
}

/* AI Status Indicator */
.ai-status {
    display: flex;
    align-items: center;
    gap: calc(var(--spacing) * 1);
    font-size: 12px;
    color: var(--neutral-600);
}

.status-dot {
    width: 8px;
    height: 8px;
    border-radius: 50%;
    background-color: var(--neutral-400);
    transition: background-color 0.3s ease;
}

.status-dot.online {
    background-color: var(--success);
    box-shadow: 0 0 6px rgba(16, 185, 129, 0.4);
}

.status-dot.offline {
    background-color: var(--error);
    box-shadow: 0 0 6px rgba(239, 68, 68, 0.4);
}

.status-dot.checking {
    background-color: var(--warning);
    animation: pulse 2s infinite;
}

@keyframes pulse {
    0%, 100% { opacity: 1; }
    50% { opacity: 0.5; }
}

.status-text {
    font-weight: 500;
}

/* Responsive footer */
@media (max-width: 768px) {
    .footer-content {
        flex-direction: column;
        gap: calc(var(--spacing) * 2);
    }
    
    .footer-info {
        flex-direction: column;
        gap: calc(var(--spacing) * 1);
    }
    
    .footer-separator {
        display: none;
    }
    
    .ai-status {
        order: -1;
    }
}