/* Основные переменные */
:root {
    --primary-color: #2196F3;
    --secondary-color: #64B5F6;
    --success-color: #4CAF50;
    --warning-color: #FF9800;
    --error-color: #F44336;
    --bg-color: #1a1a1a;
    --card-bg: #2d2d2d;
    --text-color: #ffffff;
    --text-secondary: #b0b0b0;
    --border-color: #404040;
    --shadow: 0 2px 10px rgba(0, 0, 0, 0.3);
    --border-radius: 12px;
    --font-size-base: 16px;
    --spacing: 16px;
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background: var(--bg-color);
    color: var(--text-color);
    font-size: var(--font-size-base);
    line-height: 1.5;
    overflow-x: hidden;
}

/* Экраны */
.screen {
    min-height: 100vh;
    padding: var(--spacing);
    opacity: 1;
    transition: opacity 0.6s ease;
}

.hidden {
    display: none !important;
}

.screen.hidden,
.loading-screen.hidden {
    display: none;
}

.screen.fade-out {
    opacity: 0;
}

/* Заставка загрузки */
.loading-screen {
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
}

.loading-spinner {
    width: 50px;
    height: 50px;
    border: 4px solid rgba(255, 255, 255, 0.3);
    border-top: 4px solid white;
    border-radius: 50%;
    animation: spin 1s linear infinite;
    margin-bottom: var(--spacing);
}

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

/* Заголовки */
.app-header {
    text-align: center;
    margin-bottom: calc(var(--spacing) * 2);
    padding: var(--spacing);
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    border-radius: var(--border-radius);
}

.app-header h1 {
    font-size: 28px;
    font-weight: 700;
    margin-bottom: 8px;
}

.app-header h1 i {
    color: #FFD54F;
    margin-right: 8px;
}

.user-info {
    color: rgba(255, 255, 255, 0.9);
    font-size: 14px;
}

.screen-header {
    display: flex;
    align-items: center;
    margin-bottom: var(--spacing);
    padding: var(--spacing) 0;
}

.screen-header h2 {
    flex: 1;
    text-align: center;
    font-size: 20px;
    font-weight: 600;
}

.btn-back {
    background: var(--card-bg);
    border: none;
    color: var(--text-color);
    width: 40px;
    height: 40px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: all 0.3s ease;
}

.btn-back:hover {
    background: var(--border-color);
    transform: scale(1.1);
}

/* Карточка статистики */
.stats-card {
    background: var(--card-bg);
    border-radius: var(--border-radius);
    padding: var(--spacing);
    margin-bottom: calc(var(--spacing) * 2);
    display: flex;
    justify-content: space-around;
    box-shadow: var(--shadow);
}

.stat-item {
    text-align: center;
    flex: 1;
}

.stat-number {
    display: block;
    font-size: 24px;
    font-weight: 700;
    color: var(--primary-color);
    margin-bottom: 4px;
}

.stat-label {
    font-size: 12px;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

/* Кнопки */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 12px 24px;
    border: none;
    border-radius: var(--border-radius);
    font-size: 16px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    text-decoration: none;
    gap: 8px;
    min-height: 48px;
}

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

.btn-primary:hover {
    background: var(--secondary-color);
    transform: translateY(-2px);
    box-shadow: 0 4px 15px rgba(33, 150, 243, 0.4);
}

.btn-secondary {
    background: var(--card-bg);
    color: var(--text-color);
    border: 1px solid var(--border-color);
}

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

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

.btn-success:hover {
    background: #45a049;
    transform: translateY(-2px);
    box-shadow: 0 4px 15px rgba(76, 175, 80, 0.4);
}

.btn-admin {
    background: linear-gradient(135deg, #6a11cb, #2575fc);
    color: white;
    border: none;
}

.btn-admin:hover {
    background: linear-gradient(135deg, #7c3aed, #3b82f6);
    transform: translateY(-2px);
    box-shadow: 0 4px 15px rgba(106, 17, 203, 0.4);
}

.action-buttons {
    display: flex;
    flex-direction: column;
    gap: var(--spacing);
    margin-bottom: calc(var(--spacing) * 2);
}

.action-buttons .btn {
    width: 100%;
}

/* Прогресс бар */
.progress-bar {
    background: var(--card-bg);
    border-radius: 25px;
    height: 8px;
    overflow: hidden;
    margin-bottom: var(--spacing);
}

.progress-fill {
    background: linear-gradient(90deg, var(--primary-color), var(--secondary-color));
    height: 100%;
    border-radius: 25px;
    transition: width 0.6s ease;
    width: 0%;
}

/* Курсы */
.courses-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
    gap: 24px;
    padding: 20px;
    max-width: 1200px;
    margin: 0 auto;
}

.course-card {
    background: linear-gradient(135deg, var(--card-bg) 0%, rgba(255, 255, 255, 0.05) 100%);
    border: 1px solid var(--border-color);
    border-radius: 20px;
    padding: 30px;
    color: var(--text-color);
    cursor: pointer;
    transition: all 0.4s ease;
    position: relative;
    overflow: hidden;
    backdrop-filter: blur(10px);
}

.course-card:hover {
    transform: translateY(-8px) scale(1.02);
    box-shadow: 0 20px 40px rgba(33, 150, 243, 0.2);
    border-color: var(--primary-color);
}

.course-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: linear-gradient(135deg, rgba(33, 150, 243, 0.1) 0%, transparent 100%);
    opacity: 0;
    transition: opacity 0.4s ease;
}

.course-card:hover::before {
    opacity: 1;
}

.course-icon {
    font-size: 3.5rem;
    margin-bottom: 20px;
    display: block;
    color: var(--primary-color);
    text-shadow: 0 2px 10px rgba(33, 150, 243, 0.3);
}

.course-logo {
    width: 60px;
    height: 60px;
    object-fit: contain;
    margin-bottom: 20px;
    border-radius: 8px;
    transition: transform 0.3s ease;
    display: block;
    margin: 0 auto 20px 0;
    float: none;
}

.course-name {
    font-size: 1.6rem;
    font-weight: 700;
    margin-bottom: 12px;
    color: var(--text-color);
}

.course-description {
    font-size: 0.95rem;
    color: var(--text-secondary);
    margin-bottom: 20px;
    line-height: 1.6;
}

.course-stats {
    display: flex;
    justify-content: space-between;
    font-size: 0.85rem;
    color: var(--text-secondary);
    margin-bottom: 16px;
}

.course-stats span {
    background: rgba(33, 150, 243, 0.1);
    padding: 4px 12px;
    border-radius: 20px;
    border: 1px solid rgba(33, 150, 243, 0.2);
}

.course-progress {
    background: var(--border-color);
    height: 6px;
    border-radius: 3px;
    margin-top: 16px;
    overflow: hidden;
    position: relative;
}

.course-progress-fill {
    background: linear-gradient(90deg, var(--success-color), #66BB6A);
    height: 100%;
    transition: width 0.5s ease;
    border-radius: 3px;
}

.course-progress-info {
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-size: 0.8rem;
    color: var(--text-secondary);
    margin-bottom: 8px;
}

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

.progress-percent {
    font-weight: 600;
    color: var(--primary-color);
}

/* Бейджи сложности задач */
.badge {
    display: inline-block;
    padding: 4px 10px;
    border-radius: 12px;
    font-size: 12px;
    font-weight: 600;
    border: 1px solid var(--border-color);
    background: var(--card-bg);
    text-transform: lowercase;
}

.badge-easy {
    background: rgba(76, 175, 80, 0.15);
    color: var(--success-color);
    border-color: var(--success-color);
}

.badge-medium {
    background: rgba(255, 152, 0, 0.15);
    color: var(--warning-color);
    border-color: var(--warning-color);
}

.badge-hard {
    background: rgba(244, 67, 54, 0.15);
    color: var(--error-color);
    border-color: var(--error-color);
}

/* Бейджи статуса задач */
.badge-pending {
    background: rgba(255, 152, 0, 0.15);
    color: var(--warning-color);
    border-color: var(--warning-color);
}

.badge-success {
    background: rgba(76, 175, 80, 0.15);
    color: var(--success-color);
    border-color: var(--success-color);
}

.badge-danger {
    background: rgba(244, 67, 54, 0.15);
    color: var(--error-color);
    border-color: var(--error-color);
}

/* Контейнер для бейджей в карточке задачи */
.lesson-badges {
    display: flex;
    gap: 8px;
    flex-wrap: wrap;
    align-items: center;
}

.course-completed {
    border-color: var(--success-color) !important;
    background: linear-gradient(135deg, var(--card-bg), rgba(76, 175, 80, 0.1));
}

.course-completed::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 4px;
    height: 100%;
    background: var(--success-color);
}

.course-trophy {
    color: #FFD700;
    margin-left: 8px;
    font-size: 1.2rem;
    animation: trophy-glow 2s ease-in-out infinite alternate;
}

@keyframes trophy-glow {
    from { text-shadow: 0 0 5px #FFD700; }
    to { text-shadow: 0 0 15px #FFD700, 0 0 25px #FFD700; }
}

/* Экран завершения курса */
.course-completion-content {
    text-align: center;
    padding: 40px 20px;
    max-width: 600px;
    margin: 0 auto;
}

.completion-animation {
    position: relative;
    margin-bottom: 40px;
}

.completion-trophy {
    font-size: 5rem;
    color: #FFD700;
    animation: trophy-bounce 2s ease-in-out infinite;
    text-shadow: 0 0 20px #FFD700;
}

.completion-sparkles {
    position: absolute;
    top: 0;
    left: 50%;
    transform: translateX(-50%);
    width: 200px;
    height: 200px;
}

.sparkle {
    position: absolute;
    color: #FFD700;
    font-size: 1rem;
    animation: sparkle 3s ease-in-out infinite;
}

.sparkle-1 { top: 10%; left: 20%; animation-delay: 0s; }
.sparkle-2 { top: 20%; right: 15%; animation-delay: 0.5s; }
.sparkle-3 { bottom: 30%; left: 10%; animation-delay: 1s; }
.sparkle-4 { bottom: 20%; right: 20%; animation-delay: 1.5s; }
.sparkle-5 { top: 50%; left: 5%; animation-delay: 2s; }

@keyframes trophy-bounce {
    0%, 20%, 50%, 80%, 100% { transform: translateY(0); }
    40% { transform: translateY(-20px); }
    60% { transform: translateY(-10px); }
}

@keyframes sparkle {
    0%, 100% { opacity: 0; transform: scale(0.5) rotate(0deg); }
    50% { opacity: 1; transform: scale(1) rotate(180deg); }
}

.completion-title {
    font-size: 2.5rem;
    color: var(--primary-color);
    margin-bottom: 16px;
    font-weight: 700;
}

.completion-subtitle {
    font-size: 1.5rem;
    color: var(--text-color);
    margin-bottom: 32px;
    font-weight: 500;
}

.completion-stats {
    display: flex;
    flex-direction: column;
    gap: 16px;
    margin-bottom: 32px;
    padding: 24px;
    background: var(--card-bg);
    border-radius: var(--border-radius);
    border: 1px solid var(--success-color);
}

.completion-stat {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 12px;
    background: rgba(76, 175, 80, 0.1);
    border-radius: 8px;
}

.completion-stat i {
    color: var(--success-color);
    font-size: 1.2rem;
    width: 24px;
    text-align: center;
}

.completion-stat span {
    color: var(--text-color);
    font-weight: 500;
}

.completion-message {
    background: var(--card-bg);
    padding: 24px;
    border-radius: var(--border-radius);
    margin-bottom: 32px;
    border-left: 4px solid var(--primary-color);
}

.completion-message p {
    color: var(--text-secondary);
    line-height: 1.6;
    margin: 0;
}

.completion-buttons {
    display: flex;
    gap: 16px;
    justify-content: center;
    flex-wrap: wrap;
}

.completion-buttons .btn {
    min-width: 180px;
}

@media (max-width: 480px) {
    .completion-title {
        font-size: 2rem;
    }
    
    .completion-subtitle {
        font-size: 1.2rem;
    }
    
    .completion-trophy {
        font-size: 4rem;
    }
    
    .completion-buttons {
        flex-direction: column;
    }
    
    .completion-buttons .btn {
        min-width: auto;
        width: 100%;
    }
}

/* Список уроков */
.lessons-container {
    display: flex;
    flex-direction: column;
    gap: var(--spacing);
    padding: 20px;
}

.loading-message {
    text-align: center;
    padding: 40px 20px;
    color: #999;
}

/* Панель фильтров задач */
.tasks-filters {
    display: flex;
    gap: 12px;
    align-items: center;
    flex-wrap: wrap;
    background: var(--card-bg);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    padding: 10px 12px;
    margin-bottom: 16px;
}
.tasks-filters label {
    color: var(--text-secondary);
    font-size: 14px;
}
.tasks-filters select {
    background: var(--bg-color);
    color: var(--text-color);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 6px 10px;
}

.lesson-card {
    background: var(--card-bg);
    border-radius: var(--border-radius);
    padding: var(--spacing);
    cursor: pointer;
    transition: all 0.3s ease;
    border: 1px solid var(--border-color);
    position: relative;
    overflow: hidden;
}

.lesson-card:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow);
    border-color: var(--primary-color);
}

.lesson-card.completed {
    border-color: var(--success-color);
}

.lesson-card.completed::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 4px;
    height: 100%;
    background: var(--success-color);
}

.lesson-number {
    display: inline-block;
    background: var(--primary-color);
    color: white;
    width: 30px;
    height: 30px;
    border-radius: 50%;
    text-align: center;
    line-height: 30px;
    font-weight: 600;
    font-size: 14px;
    margin-right: 12px;
}

.lesson-card.completed .lesson-number {
    background: var(--success-color);
}

.lesson-card.locked {
    opacity: 0.5;
    cursor: not-allowed;
    background: #2a2a2a;
}

.lesson-card.locked:hover {
    transform: none;
    box-shadow: none;
    border-color: var(--border-color);
}

.lesson-card.locked .lesson-number {
    background: #666;
    position: relative;
}

.lesson-card.locked .lesson-number::after {
    content: '\f023';
    font-family: 'Font Awesome 6 Free';
    font-weight: 900;
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    font-size: 12px;
}

.lesson-title {
    font-size: 18px;
    font-weight: 600;
    margin-bottom: 8px;
    color: var(--text-color);
}

.lesson-description {
    color: var(--text-secondary);
    font-size: 14px;
    line-height: 1.4;
}

.lock-message {
    color: #999;
    font-size: 12px;
    font-style: italic;
    margin-top: 5px;
}

/* Содержимое урока */
.lesson-content {
    max-width: 100%;
    padding-bottom: 180px; /* Еще больше отступ для ДЗ */
}

.lesson-body {
    background: linear-gradient(135deg, var(--card-bg), rgba(255, 255, 255, 0.02));
    border-radius: 16px;
    padding: 30px;
    margin-bottom: 30px;
    line-height: 1.8;
    box-shadow: 0 8px 32px rgba(0, 0, 0, 0.3);
    border: 1px solid rgba(255, 255, 255, 0.1);
    backdrop-filter: blur(10px);
}

.lesson-body h2, .lesson-body h3 {
    color: var(--primary-color);
    margin: 30px 0 15px 0;
    font-weight: 600;
    position: relative;
    padding-left: 20px;
}

.lesson-body h2::before, .lesson-body h3::before {
    content: '🔹';
    position: absolute;
    left: 0;
    top: 0;
    font-size: 16px;
}

.lesson-body h2:first-child, .lesson-body h3:first-child {
    margin-top: 0;
}

.lesson-body p {
    margin-bottom: 16px;
    text-align: justify;
    color: rgba(255, 255, 255, 0.9);
}

.lesson-body strong {
    color: var(--primary-color);
    font-weight: 600;
}

.lesson-body em {
    color: #ffc107;
    font-style: italic;
}

/* Блоки кода */
.lesson-body pre {
    background: linear-gradient(135deg, #1e1e1e, #2d2d2d);
    border: 1px solid #404040;
    border-radius: 12px;
    padding: 20px;
    overflow-x: auto;
    margin: 20px 0;
    font-family: 'Fira Code', 'Consolas', 'Monaco', 'Courier New', monospace;
    font-size: 14px;
    line-height: 1.6;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.3);
    position: relative;
}

.lesson-body pre::before {
    content: '💻 Python';
    position: absolute;
    top: 8px;
    right: 60px;
    font-size: 11px;
    color: #888;
    font-family: system-ui, -apple-system, sans-serif;
    font-weight: normal;
    text-transform: none;
}

.lesson-body pre::after {
    content: '📋';
    position: absolute;
    top: 8px;
    right: 12px;
    font-size: 16px;
    color: #888;
    cursor: pointer;
    transition: all 0.2s ease;
    opacity: 0.7;
}

.lesson-body pre:hover::after {
    opacity: 1;
    transform: scale(1.1);
    color: var(--primary-color);
}

.lesson-body code {
    background: linear-gradient(135deg, #2d2d2d, #3d3d3d);
    color: #f8f8f2;
    padding: 4px 8px;
    border-radius: 6px;
    font-family: 'Fira Code', 'Consolas', 'Monaco', 'Courier New', monospace;
    font-size: 13px;
    border: 1px solid #404040;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.2);
}

/* Подсветка синтаксиса Python */
.lesson-body pre code {
    background: none;
    padding: 0;
    border: none;
    box-shadow: none;
    font-size: 14px;
}

/* Python синтаксис */
.python-keyword {
    color: #ff79c6;
    font-weight: 600;
    font-size: inherit;
}

.python-string {
    color: #f1fa8c;
    font-size: inherit;
}

.python-comment {
    color: #6272a4;
    font-style: italic;
    font-size: inherit;
}

.python-function {
    color: #8be9fd;
    font-size: inherit;
}

.python-number {
    color: #bd93f9;
    font-size: inherit;
}

.lesson-body ul, .lesson-body ol {
    margin-left: 0;
    margin-bottom: 20px;
    padding-left: 0;
}

.lesson-body ul li {
    margin-bottom: 12px;
    padding-left: 25px;
    position: relative;
    color: rgba(255, 255, 255, 0.9);
}

.lesson-body ul li::before {
    content: '✨';
    position: absolute;
    left: 0;
    top: 0;
    font-size: 14px;
}

.lesson-body ol li {
    margin-bottom: 12px;
    padding-left: 25px;
    position: relative;
    color: rgba(255, 255, 255, 0.9);
    counter-increment: list-counter;
}

.lesson-body ol {
    counter-reset: list-counter;
}

.lesson-body ol li::before {
    content: counter(list-counter) '.';
    position: absolute;
    left: 0;
    top: 0;
    font-weight: bold;
    color: var(--primary-color);
}

/* Домашнее задание */
.homework-section {
    background: linear-gradient(135deg, rgba(76, 175, 80, 0.1), rgba(139, 195, 74, 0.1));
    border: 1px solid var(--success-color);
    border-radius: var(--border-radius);
    padding: calc(var(--spacing) * 1.5);
    margin-bottom: calc(var(--spacing) * 3);
    box-shadow: var(--shadow);
}

.homework-section h3 {
    color: var(--success-color);
    margin-bottom: var(--spacing);
    display: flex;
    align-items: center;
    gap: 8px;
}

.homework-section p {
    margin-bottom: var(--spacing);
}

.homework-task {
    background: rgba(255, 255, 255, 0.05);
    border-radius: var(--border-radius);
    padding: var(--spacing);
    margin-bottom: calc(var(--spacing) * 1.5);
    border-left: 4px solid var(--success-color);
}

/* Статусы домашнего задания */
.homework-status {
    display: flex;
    align-items: flex-start;
    gap: 15px;
    padding: calc(var(--spacing) * 1.5);
    border-radius: var(--border-radius);
    margin: calc(var(--spacing) * 1.5) 0;
    animation: fadeIn 0.5s ease-in-out;
}

.homework-status-pending {
    background: linear-gradient(135deg, rgba(255, 193, 7, 0.1), rgba(255, 235, 59, 0.1));
    border: 1px solid #ffc107;
}

.homework-status-approved {
    background: linear-gradient(135deg, rgba(76, 175, 80, 0.1), rgba(139, 195, 74, 0.1));
    border: 1px solid var(--success-color);
}

.homework-status-rejected {
    background: linear-gradient(135deg, rgba(244, 67, 54, 0.1), rgba(255, 87, 34, 0.1));
    border: 1px solid var(--error-color);
}

.status-icon {
    font-size: 24px;
    min-width: 30px;
    text-align: center;
}

.status-content {
    flex: 1;
}

.status-content h4 {
    margin: 0 0 8px 0;
    font-size: 16px;
}

.status-content p {
    margin: 0 0 8px 0;
    font-size: 14px;
    line-height: 1.4;
}

.success-message {
    color: var(--success-color);
    font-weight: 500;
}

.error-message {
    color: var(--error-color);
    font-weight: 500;
}

/* Анимация загрузки */
.loading-dots {
    display: flex;
    gap: 4px;
    margin-top: 8px;
}

.loading-dots span {
    width: 8px;
    height: 8px;
    background: #ffc107;
    border-radius: 50%;
    animation: bounce 1.4s ease-in-out infinite both;
}

.loading-dots span:nth-child(1) { animation-delay: -0.32s; }
.loading-dots span:nth-child(2) { animation-delay: -0.16s; }

@keyframes bounce {
    0%, 80%, 100% {
        transform: scale(0);
    }
    40% {
        transform: scale(1);
    }
}

/* Эффекты для интерактивности */
.lesson-body pre {
    transition: all 0.3s ease;
}

.lesson-body pre:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 25px rgba(0, 0, 0, 0.4);
}

.lesson-body code {
    transition: all 0.2s ease;
}

.lesson-body code:hover {
    transform: scale(1.05);
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.3);
}

/* Анимация появления элементов */
.lesson-body h2, .lesson-body h3 {
    animation: slideInLeft 0.6s ease-out;
}

.lesson-body p {
    animation: fadeInUp 0.8s ease-out;
}

.lesson-body pre {
    animation: slideInRight 0.7s ease-out;
}

@keyframes slideInLeft {
    from {
        opacity: 0;
        transform: translateX(-30px);
    }
    to {
        opacity: 1;
        transform: translateX(0);
    }
}

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

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

/* Форма отправки домашнего задания */
.homework-submission, .homework-resubmit {
    background: rgba(255, 255, 255, 0.02);
    border-radius: var(--border-radius);
    padding: calc(var(--spacing) * 1.5);
    margin-top: calc(var(--spacing) * 1.5);
    border: 1px solid rgba(255, 255, 255, 0.1);
}

.homework-submission h4, .homework-resubmit h4 {
    margin: 0 0 var(--spacing) 0;
    color: var(--primary-color);
    font-size: 16px;
}

.homework-submission textarea, .homework-resubmit textarea {
    width: 100%;
    min-height: 120px;
    background: var(--input-bg);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    padding: 12px;
    color: var(--text-primary);
    font-family: 'Courier New', monospace;
    font-size: 14px;
    resize: vertical;
    margin-bottom: var(--spacing);
}

.homework-submission textarea:focus, .homework-resubmit textarea:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 2px rgba(33, 150, 243, 0.2);
}

.file-upload {
    margin-bottom: var(--spacing);
}

.file-upload label {
    display: block;
    margin-bottom: 8px;
    font-size: 14px;
    color: var(--text-secondary);
}

.file-upload input[type="file"] {
    width: 100%;
    padding: 10px;
    background: var(--input-bg);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    color: var(--text-primary);
    font-size: 14px;
}

.file-upload input[type="file"]:focus {
    outline: none;
    border-color: var(--primary-color);
}

/* Анимация пульсации для привлечения внимания */
@keyframes pulse {
    0% {
        box-shadow: 0 0 0 0 rgba(33, 150, 243, 0.7);
    }
    70% {
        box-shadow: 0 0 0 10px rgba(33, 150, 243, 0);
    }
    100% {
        box-shadow: 0 0 0 0 rgba(33, 150, 243, 0);
    }
}

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

/* Навигация по урокам */
.lesson-navigation {
    position: fixed;
    bottom: 0;
    left: 0;
    right: 0;
    background: var(--card-bg);
    padding: calc(var(--spacing) * 1.5);
    display: flex;
    gap: 12px;
    border-top: 1px solid var(--border-color);
    box-shadow: 0 -2px 10px rgba(0, 0, 0, 0.3);
    min-height: 80px;
}

.lesson-navigation .btn {
    flex: 1;
    padding: 12px 8px;
    font-size: 14px;
}

/* Экран успеха */
.success-content {
    text-align: center;
    padding: calc(var(--spacing) * 4) var(--spacing);
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    min-height: 70vh;
}

.success-icon {
    font-size: 80px;
    color: var(--success-color);
    margin-bottom: calc(var(--spacing) * 2);
    animation: bounce 1s ease-in-out;
}

@keyframes bounce {
    0%, 20%, 50%, 80%, 100% {
        transform: translateY(0);
    }
    40% {
        transform: translateY(-20px);
    }
    60% {
        transform: translateY(-10px);
    }
}

.success-content h2 {
    font-size: 28px;
    margin-bottom: var(--spacing);
    color: var(--success-color);
}

.success-content p {
    color: var(--text-secondary);
    margin-bottom: calc(var(--spacing) * 2);
    font-size: 16px;
}

.success-buttons {
    display: flex;
    flex-direction: column;
    gap: var(--spacing);
    width: 100%;
    max-width: 300px;
}

/* Адаптивность */
@media (max-width: 480px) {
    :root {
        --spacing: 12px;
        --font-size-base: 14px;
    }
    
    .app-header h1 {
        font-size: 24px;
    }
    
    .stats-card {
        flex-direction: column;
        gap: var(--spacing);
    }
    
    .stat-item {
        flex: none;
    }
    
    .lesson-navigation {
        flex-direction: column;
    }
    
    .lesson-navigation .btn {
        flex: none;
    }
}

/* Скрытие полос прокрутки для WebKit */
::-webkit-scrollbar {
    width: 6px;
}

::-webkit-scrollbar-track {
    background: var(--card-bg);
}

::-webkit-scrollbar-thumb {
    background: var(--border-color);
    border-radius: 3px;
}

::-webkit-scrollbar-thumb:hover {
    background: var(--primary-color);
}

/* Секция админ панели на экране курсов */
.admin-panel-section {
    margin-top: calc(var(--spacing) * 2);
    text-align: center;
    padding: var(--spacing);
}

.admin-panel-section .btn-admin {
    background: linear-gradient(135deg, #FF6B35, #F7931E);
    color: white;
    border: none;
    padding: 12px 24px;
    border-radius: var(--border-radius);
    font-weight: 600;
    box-shadow: 0 4px 15px rgba(255, 107, 53, 0.3);
    transition: all 0.3s ease;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    font-size: 14px;
}

.admin-panel-section .btn-admin:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(255, 107, 53, 0.4);
    background: linear-gradient(135deg, #F7931E, #FF6B35);
}

/* Стили для аттестации */
.assessment-content {
    padding: 20px;
    max-width: 800px;
    margin: 0 auto;
}

.assessment-description,
.assessment-rules {
    background: var(--card-bg);
    border-radius: var(--border-radius);
    padding: 20px;
    margin-bottom: 20px;
}

.assessment-description h3,
.assessment-rules h3 {
    color: var(--primary-color);
    margin-bottom: 15px;
}

.assessment-rules ul {
    list-style: none;
    padding: 0;
}

.assessment-rules li {
    padding: 8px 0;
    border-bottom: 1px solid var(--border-color);
}

.assessment-rules li:last-child {
    border-bottom: none;
}

.questions-container,
.practical-container {
    background: var(--card-bg);
    border-radius: var(--border-radius);
    padding: 20px;
    margin-bottom: 20px;
}

.question-block {
    margin-bottom: 30px;
    padding: 20px;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
}

.question-block h4 {
    color: var(--primary-color);
    margin-bottom: 10px;
}

.question-options {
    margin-top: 15px;
}

.option-label {
    display: block;
    margin-bottom: 10px;
    padding: 10px;
    background: var(--bg-color);
    border-radius: var(--border-radius);
    cursor: pointer;
    transition: background-color 0.3s;
}

.option-label:hover {
    background: var(--primary-color);
    color: white;
}

.option-label input[type="radio"] {
    margin-right: 10px;
}

.practical-task {
    margin-bottom: 30px;
    padding: 20px;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
}

.practical-task h4 {
    color: var(--primary-color);
    margin-bottom: 10px;
}

.practical-answer {
    width: 100%;
    min-height: 120px;
    padding: 15px;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    background: var(--bg-color);
    color: var(--text-color);
    font-family: monospace;
    font-size: 14px;
    resize: vertical;
    margin-top: 10px;
}

.practical-answer:focus {
    outline: none;
    border-color: var(--primary-color);
}

.assessment-navigation {
    display: flex;
    justify-content: space-between;
    gap: 15px;
    margin-top: 30px;
    padding: 20px;
}

.assessment-results {
    padding: 20px;
    max-width: 600px;
    margin: 0 auto;
}

.result-header {
    text-align: center;
    padding: 30px;
    border-radius: var(--border-radius);
    margin-bottom: 30px;
}

.result-header.success {
    background: var(--success-color);
    color: white;
}

.result-header.failure {
    background: var(--error-color);
    color: white;
}

.result-header i {
    font-size: 3rem;
    margin-bottom: 15px;
}

.score-breakdown {
    background: var(--card-bg);
    border-radius: var(--border-radius);
    padding: 20px;
    margin-bottom: 20px;
}

.score-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 10px 0;
    border-bottom: 1px solid var(--border-color);
}

.score-item:last-child {
    border-bottom: none;
}

.score-label {
    font-weight: bold;
}

.score-value {
    color: var(--primary-color);
    font-weight: bold;
    font-size: 1.2rem;
}

.ai-feedback {
    background: var(--card-bg);
    border-radius: var(--border-radius);
    padding: 20px;
    margin-bottom: 20px;
}

.ai-feedback h3 {
    color: var(--primary-color);
    margin-bottom: 15px;
}

.result-actions {
    display: flex;
    gap: 15px;
    justify-content: center;
}

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

.btn-warning:hover {
    background: #e68900;
    transform: translateY(-2px);
    box-shadow: 0 4px 15px rgba(255, 152, 0, 0.4);
}

/* Дополнительные адаптивные стили для аттестации */
@media (max-width: 768px) {
    .assessment-navigation {
        flex-direction: column;
    }
    
    .assessment-navigation .btn {
        width: 100%;
    }
    
    .result-actions {
        flex-direction: column;
    }
    
    .result-actions .btn {
        width: 100%;
    }
    
    .assessment-content {
        padding: 15px;
    }
    
    .question-block,
    .practical-task {
        padding: 15px;
    }
}

/* Загрузка файлов в аттестации */
.file-upload-section {
    margin-top: 15px;
    padding: 10px;
    background: rgba(255, 255, 255, 0.05);
    border-radius: var(--border-radius);
    border: 1px dashed var(--border-color);
}

.file-upload-label {
    display: inline-block;
    padding: 8px 16px;
    background: var(--primary-color);
    color: white;
    border-radius: var(--border-radius);
    cursor: pointer;
    transition: all 0.3s;
    font-size: 14px;
}

.file-upload-label:hover {
    background: #1976d2;
    transform: translateY(-1px);
}

.file-upload-label i {
    margin-right: 8px;
}

.practical-file-input {
    display: none;
}

.file-info {
    margin-top: 10px;
}

.file-selected {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 8px 12px;
    background: var(--card-bg);
    border: 1px solid var(--success-color);
    border-radius: var(--border-radius);
    font-size: 14px;
}

.file-selected i {
    color: var(--success-color);
}

.file-name {
    flex: 1;
    font-weight: 500;
    color: var(--text-color);
}

.file-size {
    color: var(--text-color);
    opacity: 0.7;
    font-size: 12px;
}

.remove-file-btn {
    background: none;
    border: none;
    color: var(--error-color);
    cursor: pointer;
    padding: 4px;
    border-radius: var(--border-radius);
    transition: background 0.3s;
}

.remove-file-btn:hover {
    background: rgba(231, 76, 60, 0.2);
}

/* Стили для счетчика символов и улучшенных форм ДЗ */
.textarea-container {
    position: relative;
    margin-bottom: var(--spacing);
}

.textarea-container textarea {
    width: 100%;
    min-height: 120px;
    padding: 12px;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    background: var(--card-bg);
    color: var(--text-color);
    font-family: 'Courier New', monospace;
    font-size: 14px;
    line-height: 1.5;
    resize: vertical;
    transition: border-color 0.3s;
}

.textarea-container textarea:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 2px rgba(33, 150, 243, 0.2);
}

.char-counter {
    position: absolute;
    bottom: -20px;
    right: 0;
    font-size: 12px;
    color: var(--text-secondary);
    transition: color 0.3s;
}

.homework-submission .file-upload,
.homework-resubmit .file-upload {
    margin-bottom: var(--spacing);
}

.homework-submission .file-upload label,
.homework-resubmit .file-upload label {
    display: block;
    margin-bottom: 8px;
    font-weight: 500;
    color: var(--text-color);
}

.homework-submission .file-upload input,
.homework-resubmit .file-upload input {
    width: 100%;
    padding: 8px 12px;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    background: var(--card-bg);
    color: var(--text-color);
    font-size: 14px;
    transition: border-color 0.3s;
}

.homework-submission .file-upload input:focus,
.homework-resubmit .file-upload input:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 2px rgba(33, 150, 243, 0.2);
}

.form-text {
    font-size: 12px;
    color: var(--text-secondary);
    margin-top: 4px;
    line-height: 1.4;
}

/* Улучшенные стили для статусов ДЗ */
.homework-status {
    padding: var(--spacing);
    border-radius: var(--border-radius);
    margin-bottom: var(--spacing);
    border-left: 4px solid;
}

.homework-status-pending {
    background: rgba(255, 152, 0, 0.1);
    border-left-color: var(--warning-color);
}

.homework-status-approved {
    background: rgba(76, 175, 80, 0.1);
    border-left-color: var(--success-color);
}

.homework-status-rejected {
    background: rgba(244, 67, 54, 0.1);
    border-left-color: var(--error-color);
}

.status-icon {
    font-size: 24px;
    margin-bottom: 8px;
}

.status-content h4 {
    margin: 0 0 8px 0;
    color: var(--text-color);
}

.status-content p {
    margin: 0 0 8px 0;
    color: var(--text-secondary);
    line-height: 1.5;
}

.success-message {
    color: var(--success-color) !important;
    font-weight: 500;
}

.error-message {
    color: var(--error-color) !important;
    font-weight: 500;
}

/* Анимация загрузки для проверки ДЗ */
.loading-dots {
    display: inline-flex;
    gap: 4px;
    margin-top: 8px;
}

.loading-dots span {
    width: 6px;
    height: 6px;
    background: var(--warning-color);
    border-radius: 50%;
    animation: loadingDots 1.4s infinite ease-in-out both;
}

.loading-dots span:nth-child(1) { animation-delay: -0.32s; }
.loading-dots span:nth-child(2) { animation-delay: -0.16s; }
.loading-dots span:nth-child(3) { animation-delay: 0s; }

@keyframes loadingDots {
    0%, 80%, 100% {
        transform: scale(0);
        opacity: 0.5;
    }
    40% {
        transform: scale(1);
        opacity: 1;
    }
}

/* ===== Стили для настроек таймера ===== */
.timer-settings-content {
    max-width: 600px;
    margin: 0 auto;
}

.settings-section {
    background: var(--card-bg);
    border-radius: var(--border-radius);
    padding: var(--spacing);
    margin-bottom: var(--spacing);
    border: 1px solid var(--border-color);
}

.setting-item {
    margin-bottom: 16px;
}

.setting-item:last-child {
    margin-bottom: 0;
}

.setting-label {
    display: block;
    font-weight: 500;
    margin-bottom: 8px;
    color: var(--text-color);
    cursor: pointer;
    display: flex;
    align-items: center;
    gap: 8px;
}

.setting-label input[type="checkbox"] {
    margin-right: 8px;
    transform: scale(1.2);
    accent-color: var(--primary-color);
}

.checkmark {
    font-weight: normal;
}

.setting-select,
.setting-input,
.setting-textarea {
    width: 100%;
    padding: 12px;
    background: var(--bg-color);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    color: var(--text-color);
    font-size: 14px;
    transition: border-color 0.3s ease, box-shadow 0.3s ease;
}

.setting-select:focus,
.setting-input:focus,
.setting-textarea:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 2px rgba(33, 150, 243, 0.2);
}

.setting-textarea {
    resize: vertical;
    min-height: 80px;
    font-family: inherit;
    line-height: 1.5;
}

.setting-description {
    font-size: 12px;
    color: var(--text-secondary);
    margin-top: 4px;
    line-height: 1.4;
}

.days-checkboxes {
    display: flex;
    flex-wrap: wrap;
    gap: 12px;
    margin-top: 8px;
}

.days-checkboxes label {
    display: flex;
    align-items: center;
    gap: 6px;
    font-size: 14px;
    color: var(--text-color);
    cursor: pointer;
    padding: 6px 12px;
    background: var(--bg-color);
    border: 1px solid var(--border-color);
    border-radius: 6px;
    transition: all 0.3s ease;
}

.days-checkboxes label:hover {
    background: var(--primary-color);
    border-color: var(--primary-color);
}

.days-checkboxes input[type="checkbox"] {
    margin: 0;
    transform: scale(1.1);
    accent-color: var(--primary-color);
}

.timer-actions {
    display: flex;
    gap: 12px;
    justify-content: flex-end;
    margin-top: 24px;
    padding-top: 24px;
    border-top: 1px solid var(--border-color);
}

.timer-actions .btn {
    min-width: 120px;
}

.timer-status {
    margin-top: 16px;
    padding: 12px;
    border-radius: 8px;
    font-size: 14px;
    line-height: 1.4;
}

.timer-status.success {
    background: rgba(76, 175, 80, 0.1);
    border: 1px solid var(--success-color);
    color: var(--success-color);
}

.timer-status.error {
    background: rgba(244, 67, 54, 0.1);
    border: 1px solid var(--error-color);
    color: var(--error-color);
}

.timer-status.info {
    background: rgba(33, 150, 243, 0.1);
    border: 1px solid var(--primary-color);
    color: var(--primary-color);
}

/* Адаптивность для мобильных устройств */
@media (max-width: 480px) {
    .timer-actions {
        flex-direction: column;
    }
    
    .timer-actions .btn {
        width: 100%;
    }
    
    .days-checkboxes {
        justify-content: center;
    }
    
    .days-checkboxes label {
        flex: 1;
        min-width: 45px;
        justify-content: center;
        font-size: 12px;
        padding: 8px 4px;
    }
}