:root {
    --primary-color: #2196F3;
    --secondary-color: #4CAF50;
    --warning-color: #FFC107;
    --danger-color: #F44336;
    --accent-color: #9C27B0;
    --background-color: #f5f5f5;
    --surface-color: #ffffff;
    --text-primary: #333333;
    --text-secondary: #666666;
    --border-color: #e0e0e0;
    --shadow: 0 2px 8px rgba(0,0,0,0.1);
    --shadow-hover: 0 4px 16px rgba(0,0,0,0.15);
    --border-radius: 12px;
    --transition: all 0.3s ease;
}

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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: var(--background-color);
    color: var(--text-primary);
    line-height: 1.6;
    padding-bottom: 80px;
    background-image: 
        radial-gradient(circle at 1px 1px, rgba(255,255,255,0.15) 1px, transparent 0);
    background-size: 20px 20px;
    min-height: 100vh;
}

.app-header {
    background: linear-gradient(135deg, var(--primary-color), var(--accent-color));
    color: white;
    padding: 1rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    box-shadow: var(--shadow);
    position: sticky;
    top: 0;
    z-index: 100;
}

.app-header h1 {
    font-size: 1.5rem;
    font-weight: 600;
}

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

.icon-btn {
    background: rgba(255,255,255,0.2);
    border: none;
    color: white;
    padding: 0.5rem;
    border-radius: 50%;
    cursor: pointer;
    transition: var(--transition);
    position: relative;
}

.icon-btn:hover {
    background: rgba(255,255,255,0.3);
    transform: scale(1.05);
}

.notification-badge {
    position: absolute;
    top: -5px;
    right: -5px;
    background: var(--danger-color);
    color: white;
    border-radius: 50%;
    width: 20px;
    height: 20px;
    font-size: 0.7rem;
    display: flex;
    align-items: center;
    justify-content: center;
    min-width: 20px;
}

.app-main {
    padding: 1rem;
    max-width: 1200px;
    margin: 0 auto;
}

.content-section {
    display: none;
    animation: fadeIn 0.3s ease-in;
}

.content-section.active {
    display: block;
}

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

.welcome-card {
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    color: white;
    padding: 2rem;
    border-radius: var(--border-radius);
    margin-bottom: 1.5rem;
    text-align: center;
    box-shadow: var(--shadow);
}

.welcome-card h2 {
    margin-bottom: 0.5rem;
    font-size: 1.5rem;
}

.quick-actions {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1rem;
    margin-bottom: 1.5rem;
}

.action-btn {
    background: var(--surface-color);
    border: 2px solid var(--border-color);
    padding: 1rem;
    border-radius: var(--border-radius);
    cursor: pointer;
    transition: var(--transition);
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.5rem;
    font-size: 0.9rem;
    font-weight: 500;
    text-decoration: none;
    color: var(--text-primary);
}

.action-btn:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-hover);
}

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

.action-btn.secondary {
    background: var(--secondary-color);
    color: white;
    border-color: var(--secondary-color);
}

.action-btn i {
    font-size: 1.5rem;
}

.stats-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 1rem;
    margin-bottom: 1.5rem;
}

.stat-card {
    background: var(--surface-color);
    padding: 1.5rem;
    border-radius: var(--border-radius);
    text-align: center;
    box-shadow: var(--shadow);
    border: 1px solid var(--border-color);
}

.stat-number {
    font-size: 2rem;
    font-weight: bold;
    color: var(--primary-color);
    margin-bottom: 0.5rem;
}

.stat-label {
    font-size: 0.8rem;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.recent-activity {
    background: var(--surface-color);
    padding: 1.5rem;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow);
}

.recent-activity h3 {
    margin-bottom: 1rem;
    color: var(--text-primary);
}

.activity-list {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.activity-item {
    padding: 1rem;
    background: var(--background-color);
    border-radius: 8px;
    border-left: 4px solid var(--primary-color);
}

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

.empty-state i {
    font-size: 3rem;
    margin-bottom: 1rem;
    opacity: 0.5;
}

.profile-header {
    text-align: center;
    margin-bottom: 2rem;
    position: relative;
}

.profile-avatar {
    width: 100px;
    height: 100px;
    margin: 0 auto 1rem;
    border-radius: 50%;
    background: var(--primary-color);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 4rem;
    color: white;
    box-shadow: var(--shadow);
}

.edit-btn {
    position: absolute;
    top: 0;
    right: 0;
    background: var(--secondary-color);
    color: white;
    border: none;
    padding: 0.5rem;
    border-radius: 50%;
    cursor: pointer;
    transition: var(--transition);
}

.edit-btn:hover {
    transform: scale(1.1);
}

.profile-form {
    background: var(--surface-color);
    padding: 2rem;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow);
}

.form-group {
    margin-bottom: 1.5rem;
}

.form-group label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 500;
    color: var(--text-primary);
}

.form-group input,
.form-group select,
.form-group textarea {
    width: 100%;
    padding: 0.75rem;
    border: 2px solid var(--border-color);
    border-radius: 8px;
    font-size: 1rem;
    transition: var(--transition);
    background: var(--surface-color);
}

.form-group input:focus,
.form-group select:focus,
.form-group textarea:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(33, 150, 243, 0.1);
}

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

.submit-btn {
    background: var(--primary-color);
    color: white;
    border: none;
    padding: 1rem 2rem;
    border-radius: var(--border-radius);
    cursor: pointer;
    font-size: 1rem;
    font-weight: 500;
    transition: var(--transition);
    display: flex;
    align-items: center;
    gap: 0.5rem;
    margin: 0 auto;
}

.submit-btn:hover {
    background: #1976D2;
    transform: translateY(-2px);
    box-shadow: var(--shadow-hover);
}

.video-container {
    background: var(--surface-color);
    border-radius: var(--border-radius);
    padding: 1rem;
    margin-bottom: 1rem;
    box-shadow: var(--shadow);
}

.video-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1rem;
    margin-bottom: 1rem;
}

.video-wrapper {
    position: relative;
    aspect-ratio: 16/9;
    background: #000;
    border-radius: 8px;
    overflow: hidden;
}

.video-wrapper video {
    width: 100%;
    height: 100%;
    object-fit: cover;
}

.video-label {
    position: absolute;
    bottom: 10px;
    left: 10px;
    background: rgba(0,0,0,0.7);
    color: white;
    padding: 0.25rem 0.5rem;
    border-radius: 4px;
    font-size: 0.8rem;
}

.call-controls {
    display: flex;
    justify-content: center;
    gap: 1rem;
    margin-bottom: 1rem;
}

.control-btn {
    width: 50px;
    height: 50px;
    border-radius: 50%;
    border: none;
    cursor: pointer;
    transition: var(--transition);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.2rem;
}

.control-btn.audio-on,
.control-btn.video-on {
    background: var(--secondary-color);
    color: white;
}

.control-btn.audio-off,
.control-btn.video-off {
    background: var(--danger-color);
    color: white;
}

.control-btn.end-call {
    background: var(--danger-color);
    color: white;
}

.control-btn:not(.end-call) {
    background: var(--primary-color);
    color: white;
}

.control-btn:hover {
    transform: scale(1.1);
}

.call-info {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0.5rem;
    background: var(--background-color);
    border-radius: 8px;
}

.call-timer {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-weight: 500;
}

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

.call-features {
    background: var(--surface-color);
    border-radius: var(--border-radius);
    box-shadow: var(--shadow);
    overflow: hidden;
}

.feature-tabs {
    display: flex;
    background: var(--background-color);
}

.tab-btn {
    flex: 1;
    padding: 1rem;
    border: none;
    background: transparent;
    cursor: pointer;
    transition: var(--transition);
    border-bottom: 3px solid transparent;
}

.tab-btn.active {
    background: var(--surface-color);
    border-bottom-color: var(--primary-color);
    color: var(--primary-color);
}

.tab-content {
    padding: 1.5rem;
}

.tab-panel {
    display: none;
}

.tab-panel.active {
    display: block;
}

.topics-list {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    margin-bottom: 1rem;
}

.topic-btn {
    background: var(--background-color);
    border: 1px solid var(--border-color);
    padding: 0.5rem 1rem;
    border-radius: 20px;
    cursor: pointer;
    transition: var(--transition);
    font-size: 0.9rem;
}

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

.translator-form {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.language-selector {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.language-selector select {
    flex: 1;
    padding: 0.5rem;
    border: 1px solid var(--border-color);
    border-radius: 8px;
}

.swap-btn {
    background: var(--accent-color);
    color: white;
    border: none;
    padding: 0.5rem;
    border-radius: 50%;
    cursor: pointer;
    transition: var(--transition);
}

.swap-btn:hover {
    transform: rotate(180deg);
}

.translation-result {
    background: var(--background-color);
    padding: 1rem;
    border-radius: 8px;
    border: 1px solid var(--border-color);
    min-height: 50px;
    margin-top: 1rem;
}

.pronunciation-controls {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.pronunciation-buttons {
    display: flex;
    gap: 1rem;
}

.pronunciation-feedback {
    background: var(--background-color);
    padding: 1rem;
    border-radius: 8px;
    border: 1px solid var(--border-color);
    min-height: 50px;
}

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

.matching-filters {
    background: var(--surface-color);
    padding: 1rem;
    border-radius: var(--border-radius);
    margin-bottom: 1rem;
    display: flex;
    gap: 1rem;
    align-items: end;
    box-shadow: var(--shadow);
}

.filter-group {
    flex: 1;
}

.filter-group label {
    display: block;
    margin-bottom: 0.5rem;
    font-size: 0.9rem;
    color: var(--text-secondary);
}

.partners-list {
    display: grid;
    gap: 1rem;
}

.partner-card {
    background: var(--surface-color);
    padding: 1.5rem;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow);
    cursor: pointer;
    transition: var(--transition);
    border: 1px solid var(--border-color);
}

.partner-card:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-hover);
}

.partner-header {
    display: flex;
    align-items: center;
    gap: 1rem;
    margin-bottom: 1rem;
}

.partner-avatar {
    width: 60px;
    height: 60px;
    border-radius: 50%;
    background: var(--primary-color);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
    color: white;
}

.partner-info h4 {
    margin: 0;
    color: var(--text-primary);
}

.partner-info p {
    margin: 0;
    color: var(--text-secondary);
    font-size: 0.9rem;
}

.partner-languages {
    display: flex;
    gap: 0.5rem;
    margin-top: 1rem;
}

.language-tag {
    background: var(--primary-color);
    color: white;
    padding: 0.25rem 0.5rem;
    border-radius: 12px;
    font-size: 0.8rem;
}

.cultural-categories {
    display: flex;
    gap: 0.5rem;
    margin-bottom: 1rem;
    overflow-x: auto;
    padding-bottom: 0.5rem;
}

.category-btn {
    background: var(--surface-color);
    border: 1px solid var(--border-color);
    padding: 0.5rem 1rem;
    border-radius: 20px;
    cursor: pointer;
    transition: var(--transition);
    white-space: nowrap;
    font-size: 0.9rem;
}

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

.cultural-feed {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.cultural-post {
    background: var(--surface-color);
    padding: 1.5rem;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow);
    border: 1px solid var(--border-color);
}

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

.post-info h4 {
    margin: 0 0 0.5rem 0;
    color: var(--text-primary);
}

.post-meta {
    color: var(--text-secondary);
    font-size: 0.8rem;
}

.post-category {
    background: var(--accent-color);
    color: white;
    padding: 0.25rem 0.5rem;
    border-radius: 12px;
    font-size: 0.8rem;
}

.post-content {
    line-height: 1.6;
    color: var(--text-primary);
}

.progress-overview {
    display: grid;
    gap: 1rem;
    margin-bottom: 2rem;
}

.progress-card {
    background: var(--surface-color);
    padding: 1.5rem;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow);
    text-align: center;
}

.progress-card h3 {
    margin-bottom: 1rem;
    color: var(--text-primary);
}

.progress-bar {
    width: 100%;
    height: 8px;
    background: var(--border-color);
    border-radius: 4px;
    overflow: hidden;
    margin-bottom: 0.5rem;
}

.progress-fill {
    height: 100%;
    background: linear-gradient(90deg, var(--secondary-color), var(--primary-color));
    transition: width 0.3s ease;
}

.streak-counter {
    font-size: 2rem;
    font-weight: bold;
    color: var(--warning-color);
}

.streak-counter small {
    font-size: 1rem;
    color: var(--text-secondary);
}

.level-display {
    text-align: center;
}

.level-display span {
    font-size: 1.2rem;
    font-weight: 500;
    color: var(--primary-color);
}

.level-progress {
    width: 100%;
    height: 6px;
    background: var(--border-color);
    border-radius: 3px;
    overflow: hidden;
    margin-top: 0.5rem;
}

.level-fill {
    height: 100%;
    background: linear-gradient(90deg, var(--accent-color), var(--primary-color));
    transition: width 0.3s ease;
}

.achievements-section {
    margin-bottom: 2rem;
}

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

.achievements-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 1rem;
}

.achievement-card {
    background: var(--surface-color);
    padding: 1.5rem;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow);
    text-align: center;
    border: 2px solid var(--border-color);
    transition: var(--transition);
}

.achievement-card.unlocked {
    border-color: var(--secondary-color);
    background: linear-gradient(135deg, var(--secondary-color), var(--primary-color));
    color: white;
}

.achievement-card.locked {
    opacity: 0.5;
}

.achievement-card i {
    font-size: 2rem;
    margin-bottom: 1rem;
    color: var(--warning-color);
}

.achievement-card.unlocked i {
    color: white;
}

.achievement-card h4 {
    margin-bottom: 0.5rem;
}

.progress-chart {
    background: var(--surface-color);
    padding: 1.5rem;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow);
}

.progress-chart h3 {
    margin-bottom: 1rem;
    color: var(--text-primary);
}

#progressChart {
    width: 100%;
    height: auto;
}

.faq-section {
    background: var(--surface-color);
    padding: 2rem;
    border-radius: var(--border-radius);
    margin: 2rem 0;
    box-shadow: var(--shadow);
}

.faq-section h2 {
    margin-bottom: 1.5rem;
    text-align: center;
    color: var(--text-primary);
}

.faq-container {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.faq-item {
    border: 1px solid var(--border-color);
    border-radius: 8px;
    overflow: hidden;
}

.faq-question {
    width: 100%;
    padding: 1rem;
    background: var(--background-color);
    border: none;
    text-align: left;
    cursor: pointer;
    font-size: 1rem;
    font-weight: 500;
    display: flex;
    justify-content: space-between;
    align-items: center;
    transition: var(--transition);
}

.faq-question:hover {
    background: var(--primary-color);
    color: white;
}

.faq-question[aria-expanded="true"] {
    background: var(--primary-color);
    color: white;
}

.faq-question[aria-expanded="true"] .faq-icon {
    transform: rotate(45deg);
}

.faq-icon {
    font-size: 1.2rem;
    transition: transform 0.3s ease;
}

.faq-answer {
    padding: 1rem;
    background: var(--surface-color);
    border-top: 1px solid var(--border-color);
    animation: slideDown 0.3s ease;
}

.faq-answer[hidden] {
    display: none;
}

@keyframes slideDown {
    from {
        opacity: 0;
        max-height: 0;
        padding: 0 1rem;
    }
    to {
        opacity: 1;
        max-height: 200px;
        padding: 1rem;
    }
}

.modal {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0,0,0,0.5);
    z-index: 1000;
    animation: fadeIn 0.3s ease;
}

.modal.active {
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 1rem;
}

.modal-content {
    background: var(--surface-color);
    border-radius: var(--border-radius);
    max-width: 500px;
    width: 100%;
    max-height: 90vh;
    overflow-y: auto;
    animation: slideUp 0.3s ease;
}

@keyframes slideUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

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

.modal-header h3 {
    margin: 0;
    color: var(--text-primary);
}

.close-btn {
    background: none;
    border: none;
    font-size: 1.5rem;
    cursor: pointer;
    color: var(--text-secondary);
    transition: var(--transition);
}

.close-btn:hover {
    color: var(--danger-color);
}

.modal-body {
    padding: 1.5rem;
}

.partner-profile {
    display: flex;
    gap: 1rem;
    margin-bottom: 1.5rem;
}

.partner-avatar {
    width: 80px;
    height: 80px;
    border-radius: 50%;
    background: var(--primary-color);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 2rem;
    color: white;
    flex-shrink: 0;
}

.partner-info h4 {
    margin: 0 0 0.5rem 0;
    color: var(--text-primary);
}

.partner-info p {
    margin: 0 0 0.5rem 0;
    color: var(--text-secondary);
    font-size: 0.9rem;
}

.modal-actions {
    display: flex;
    gap: 1rem;
    justify-content: center;
}

.bottom-nav {
    position: fixed;
    bottom: 0;
    left: 0;
    right: 0;
    background: var(--surface-color);
    border-top: 1px solid var(--border-color);
    display: flex;
    padding: 0.5rem 0;
    box-shadow: 0 -2px 8px rgba(0,0,0,0.1);
    z-index: 100;
}

.nav-item {
    flex: 1;
    display: flex;
    flex-direction: column;
    align-items: center;
    padding: 0.5rem;
    text-decoration: none;
    color: var(--text-secondary);
    transition: var(--transition);
    font-size: 0.8rem;
}

.nav-item.active {
    color: var(--primary-color);
}

.nav-item:hover {
    color: var(--primary-color);
    background: rgba(33, 150, 243, 0.1);
}

.nav-item i {
    font-size: 1.2rem;
    margin-bottom: 0.25rem;
}

footer {
    text-align: center;
    padding: 2rem 1rem;
    color: var(--text-secondary);
    font-size: 0.9rem;
    background: var(--surface-color);
    border-top: 1px solid var(--border-color);
    margin-top: 2rem;
}

@media (max-width: 768px) {
    .quick-actions {
        grid-template-columns: 1fr;
    }
    
    .stats-grid {
        grid-template-columns: 1fr;
    }
    
    .video-grid {
        grid-template-columns: 1fr;
    }
    
    .matching-filters {
        flex-direction: column;
        align-items: stretch;
    }
    
    .achievements-grid {
        grid-template-columns: 1fr;
    }
    
    .language-selector {
        flex-direction: column;
    }
    
    .pronunciation-buttons {
        flex-direction: column;
    }
    
    .modal-actions {
        flex-direction: column;
    }
    
    .cultural-categories {
        flex-wrap: wrap;
    }
}

@media (min-width: 769px) {
    .app-main {
        padding: 2rem;
    }
    
    .stats-grid {
        grid-template-columns: repeat(3, 1fr);
    }
    
    .progress-overview {
        grid-template-columns: repeat(3, 1fr);
    }
    
    .quick-actions {
        grid-template-columns: repeat(2, 1fr);
        max-width: 600px;
        margin: 0 auto 1.5rem;
    }
}

.recording {
    background: var(--danger-color) !important;
    animation: pulse 1s infinite;
}

@keyframes pulse {
    0% { opacity: 1; }
    50% { opacity: 0.7; }
    100% { opacity: 1; }
}

.connected {
    color: var(--secondary-color);
}

.disconnected {
    color: var(--danger-color);
}

.connecting {
    color: var(--warning-color);
}