:root {
  /* Основные цвета — тёмная тема с красными акцентами */
  --primary-bg: #0a0a0a;
  --secondary-bg: #1a1a1a;
  --card-bg: #1e1e1e;
  
  /* Акценты — красная палитра */
  --accent-primary: #ef4444;
  --accent-secondary: #991b1b;
  --accent-gradient: linear-gradient(135deg, var(--accent-primary), var(--accent-secondary));
  
  /* Текст */
  --text-primary: #f8fafc;
  --text-secondary: #cbd5e1;
  --text-muted: #94a3b8;
  
  /* Границы и тени */
  --border-color: #374151;
  --border-light: #4b5563;
  --shadow-lg: 0 10px 40px rgba(0, 0, 0, 0.6);
  --shadow-accent: rgba(239, 68, 68, 0.25);
  
  /* Статусы */
  --success: #10b981;
  --success-bg: rgba(16, 185, 129, 0.12);
  --error: #ef4444;
  --error-bg: rgba(239, 68, 68, 0.15);
  --info: #f87171;
  --info-bg: rgba(248, 113, 113, 0.12);
  --warning: #f59e0b;
  --warning-bg: rgba(245, 158, 11, 0.12);
}

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

body {
  font-family: 'Inter', system-ui, -apple-system, Segoe UI, Roboto, Arial, sans-serif;
  background: var(--primary-bg);
  color: var(--text-primary);
  line-height: 1.7;
  min-height: 100vh;
  -webkit-font-smoothing: antialiased;
}

.container {
  width: 100%;
  max-width: 1400px;
  margin: 0 auto;
  padding: 0 1.5rem;
}

/* ================= TOP BAR ================= */
.trainer-topbar {
  background: var(--secondary-bg);
  border-bottom: 2px solid var(--accent-primary);
  padding: 1rem 0;
  position: sticky;
  top: 0;
  z-index: 100;
  box-shadow: var(--shadow-lg);
  backdrop-filter: blur(10px);
}

.trainer-topbar .container {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 1rem;
  flex-wrap: wrap;
}

.trainer-title {
  color: var(--text-primary);
  font-weight: 700;
  font-size: 1.25rem;
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.trainer-title i {
  color: var(--accent-primary);
  font-size: 1.4rem;
}

.trainer-actions {
  display: flex;
  gap: 0.75rem;
  flex-wrap: wrap;
}

/* ================= КНОПКИ ================= */
.btn-trainer {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  padding: 0.65rem 1.25rem;
  border-radius: 10px;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.25s ease;
  font-size: 0.95rem;
  background: transparent;
  color: var(--text-primary);
  border: 2px solid var(--border-color);
  text-decoration: none;
  min-width: 110px;
}

.btn-trainer:hover:not(:disabled) {
  border-color: var(--accent-primary);
  color: var(--accent-primary);
  transform: translateY(-2px);
  box-shadow: 0 6px 20px var(--shadow-accent);
}

.btn-trainer:disabled {
  opacity: 0.5;
  cursor: not-allowed;
  transform: none;
  box-shadow: none;
}

.btn-trainer.primary {
  background: var(--accent-gradient);
  border-color: var(--accent-primary);
  color: #fff;
  box-shadow: 0 4px 20px var(--shadow-accent);
}

.btn-trainer.primary:hover:not(:disabled) {
  transform: translateY(-3px);
  box-shadow: 0 8px 30px var(--shadow-accent);
}

.btn-trainer.outline {
  border-color: var(--accent-primary);
  color: var(--accent-primary);
}

.btn-trainer.outline:hover:not(:disabled) {
  background: rgba(239, 68, 68, 0.1);
}

.btn-trainer.success {
  background: var(--success);
  border-color: var(--success);
  color: #fff;
}

.btn-trainer.error {
  background: var(--error);
  border-color: var(--error);
  color: #fff;
}

/* ================= LAYOUT ================= */
.trainer-layout {
  padding: 2rem 0;
}

.trainer-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 2rem;
  margin-top: 1.5rem;
}

.trainer-panel {
  background: var(--card-bg);
  border: 1px solid var(--border-color);
  border-radius: 16px;
  padding: 1.75rem;
  box-shadow: var(--shadow-lg);
  transition: transform 0.2s ease;
}

.trainer-panel:hover {
  transform: translateY(-2px);
}

.trainer-panel h2 {
  color: var(--text-primary);
  margin-bottom: 1.25rem;
  font-weight: 700;
  font-size: 1.6rem;
  padding-bottom: 0.75rem;
  border-bottom: 2px solid var(--accent-primary);
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.trainer-panel h2 i {
  color: var(--accent-primary);
}

.trainer-panel h3 {
  color: var(--text-primary);
  font-size: 1.3rem;
  margin: 1.5rem 0 1rem;
  font-weight: 600;
}

.trainer-panel p,
.trainer-panel li {
  color: var(--text-secondary);
  margin-bottom: 0.85rem;
  font-size: 1rem;
}

.trainer-panel ul,
.trainer-panel ol {
  margin-left: 1.5rem;
  margin-bottom: 1.25rem;
}

.trainer-panel ul li {
  padding-left: 0.25rem;
}

/* ================= ТЕОРИЯ ================= */
.theory-section {
  margin-bottom: 2rem;
}

.theory-content {
  line-height: 1.8;
  color: var(--text-secondary);
}

.theory-content h4 {
  color: var(--text-primary);
  margin: 1.5rem 0 0.75rem;
  font-size: 1.15rem;
  font-weight: 600;
}

.theory-content h4:first-child {
  margin-top: 0;
}

.theory-content p {
  margin-bottom: 1rem;
}

.theory-content ul {
  margin: 1rem 0;
}

.theory-content li {
  margin-bottom: 0.5rem;
}

/* Формулы и выделения */
.formula {
  display: inline-block;
  background: rgba(239, 68, 68, 0.15);
  border: 1px solid var(--accent-primary);
  border-radius: 8px;
  padding: 0.4rem 0.8rem;
  font-family: 'Courier New', monospace;
  font-weight: 600;
  color: var(--accent-primary);
  margin: 0.25rem 0;
}

.highlight {
  background: rgba(239, 68, 68, 0.2);
  padding: 0.15rem 0.4rem;
  border-radius: 4px;
  font-weight: 500;
  color: var(--text-primary);
}

.warning-box {
  background: var(--warning-bg);
  border-left: 4px solid var(--warning);
  padding: 1rem 1.25rem;
  border-radius: 0 8px 8px 0;
  margin: 1.25rem 0;
}

.warning-box h4 {
  color: var(--warning);
  margin-bottom: 0.5rem;
  font-size: 1rem;
}

/* ================= НАВИГАЦИЯ ПО УРОКАМ ================= */
.lessons-navigation {
  margin-bottom: 1.5rem;
  padding: 1.25rem;
  background: var(--secondary-bg);
  border-radius: 12px;
  border: 1px solid var(--border-color);
}

.lessons-navigation h3 {
  margin-bottom: 1rem;
  font-size: 1.1rem;
  font-weight: 600;
  color: var(--text-primary);
}

.lessons-list {
  display: flex;
  flex-wrap: wrap;
  gap: 0.6rem;
}

.lesson-link {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0.55rem 1rem;
  background: var(--primary-bg);
  border: 2px solid var(--border-color);
  border-radius: 8px;
  text-decoration: none;
  color: var(--text-secondary);
  font-size: 0.9rem;
  font-weight: 500;
  transition: all 0.2s ease;
  min-width: 50px;
  text-align: center;
}

.lesson-link:hover {
  border-color: var(--accent-primary);
  color: var(--accent-primary);
  transform: translateY(-2px);
  box-shadow: 0 4px 12px var(--shadow-accent);
}

.lesson-link.active {
  background: rgba(239, 68, 68, 0.15);
  border-color: var(--accent-primary);
  color: var(--accent-primary);
  font-weight: 600;
  box-shadow: 0 0 0 2px rgba(239, 68, 68, 0.2);
}

.lesson-link.completed {
  border-color: var(--success);
  color: var(--success);
  position: relative;
}

.lesson-link.completed::after {
  content: '✓';
  position: absolute;
  top: -5px;
  right: -5px;
  background: var(--success);
  color: #fff;
  width: 18px;
  height: 18px;
  border-radius: 50%;
  font-size: 0.7rem;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: bold;
}

/* ================= ПРОГРЕСС И ПАГИНАЦИЯ ================= */
.lesson-pagination {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin: 1.75rem 0;
  padding: 1.25rem 0;
  border-top: 1px solid var(--border-color);
  border-bottom: 1px solid var(--border-color);
  flex-wrap: wrap;
  gap: 1rem;
}

.btn-pagination {
  padding: 0.75rem 1.75rem;
  background: var(--secondary-bg);
  border: 2px solid var(--border-color);
  border-radius: 10px;
  color: var(--text-primary);
  font-weight: 600;
  cursor: pointer;
  transition: all 0.25s ease;
  min-width: 170px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
}

.btn-pagination:hover:not(:disabled) {
  border-color: var(--accent-primary);
  color: var(--accent-primary);
  transform: translateY(-2px);
  box-shadow: 0 6px 20px var(--shadow-accent);
}

.btn-pagination:disabled {
  opacity: 0.4;
  cursor: not-allowed;
  transform: none;
  box-shadow: none;
}

.progress-container {
  display: flex;
  align-items: center;
  gap: 1rem;
}

.progress-bar {
  width: 150px;
  height: 8px;
  background: var(--border-color);
  border-radius: 4px;
  overflow: hidden;
}

.progress-fill {
  height: 100%;
  background: var(--accent-gradient);
  border-radius: 4px;
  transition: width 0.3s ease;
}

.progress-text {
  font-weight: 600;
  color: var(--text-primary);
  font-size: 1rem;
  white-space: nowrap;
}

/* ================= ПОДСКАЗКИ ================= */
.hint {
  background: var(--info-bg);
  border-left: 4px solid var(--info);
  padding: 1rem 1.25rem;
  margin: 1.25rem 0;
  border-radius: 0 8px 8px 0;
}

.hint h4 {
  color: var(--info);
  margin-bottom: 0.5rem;
  font-size: 1rem;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.hint p {
  margin: 0;
  font-size: 0.95rem;
}

/* ================= ТЕСТ / QUIZ ================= */
.quiz-section {
  margin-top: 1rem;
}

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

.quiz-question {
  font-size: 1.15rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 1.25rem;
  line-height: 1.5;
}

.options-list {
  display: flex;
  flex-direction: column;
  gap: 0.85rem;
  margin-bottom: 1.5rem;
}

.option-item {
  display: flex;
  align-items: flex-start;
  gap: 0.85rem;
  padding: 1rem 1.25rem;
  border-radius: 12px;
  border: 2px solid var(--border-color);
  background: rgba(255, 255, 255, 0.03);
  cursor: pointer;
  transition: all 0.2s ease;
}

.option-item:hover {
  border-color: var(--accent-primary);
  background: rgba(239, 68, 68, 0.08);
  transform: translateX(3px);
}

.option-item input[type="radio"],
.option-item input[type="checkbox"] {
  margin-top: 4px;
  width: 18px;
  height: 18px;
  accent-color: var(--accent-primary);
  cursor: pointer;
}

.option-prefix {
  min-width: 26px;
  font-weight: 700;
  color: var(--accent-primary);
  font-size: 1rem;
}

.option-text {
  color: var(--text-secondary);
  flex: 1;
  font-size: 1rem;
  line-height: 1.5;
}

/* Состояния ответов */
.option-item.selected {
  border-color: var(--accent-primary);
  background: rgba(239, 68, 68, 0.12);
  box-shadow: 0 0 0 3px rgba(239, 68, 68, 0.15);
}

.option-item.correct {
  border-color: var(--success);
  background: var(--success-bg);
  animation: pulseSuccess 0.4s ease;
}

.option-item.incorrect {
  border-color: var(--error);
  background: var(--error-bg);
  animation: pulseError 0.4s ease;
}

@keyframes pulseSuccess {
  0% { box-shadow: 0 0 0 0 rgba(16, 185, 129, 0.4); }
  70% { box-shadow: 0 0 0 8px rgba(16, 185, 129, 0); }
  100% { box-shadow: 0 0 0 0 rgba(16, 185, 129, 0); }
}

@keyframes pulseError {
  0% { box-shadow: 0 0 0 0 rgba(239, 68, 68, 0.4); }
  70% { box-shadow: 0 0 0 8px rgba(239, 68, 68, 0); }
  100% { box-shadow: 0 0 0 0 rgba(239, 68, 68, 0); }
}

/* Блок с пояснением */
.explanation-block {
  margin-top: 1.25rem;
  padding: 1.25rem;
  border-radius: 12px;
  border: 1px dashed var(--border-light);
  background: rgba(255, 255, 255, 0.03);
  animation: fadeIn 0.3s ease;
}

.explanation-block h4 {
  color: var(--text-primary);
  margin-bottom: 0.75rem;
  font-size: 1.1rem;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.explanation-block h4 i {
  color: var(--info);
}

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

.explanation-block .formula {
  display: block;
  margin: 0.75rem 0;
  text-align: center;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(10px); }
  to { opacity: 1; transform: translateY(0); }
}

/* Кнопки действий в тесте */
.quiz-actions {
  display: flex;
  gap: 0.75rem;
  margin-top: 1.5rem;
  flex-wrap: wrap;
}

.btn-check {
  background: var(--accent-gradient);
  border: none;
  color: #fff;
  padding: 0.75rem 2rem;
  border-radius: 10px;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.25s ease;
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
}

.btn-check:hover:not(:disabled) {
  transform: translateY(-2px);
  box-shadow: 0 8px 25px var(--shadow-accent);
}

.btn-check:disabled {
  opacity: 0.6;
  cursor: not-allowed;
  transform: none;
}

.btn-next {
  background: var(--secondary-bg);
  border: 2px solid var(--border-color);
  color: var(--text-primary);
  padding: 0.75rem 2rem;
  border-radius: 10px;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.25s ease;
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
}

.btn-next:hover:not(:disabled) {
  border-color: var(--accent-primary);
  color: var(--accent-primary);
  transform: translateY(-2px);
}

/* Статус результата */
.quiz-result {
  margin-top: 1.5rem;
  padding: 1.25rem;
  border-radius: 12px;
  text-align: center;
  font-weight: 600;
}

.quiz-result.success {
  background: var(--success-bg);
  border: 1px solid var(--success);
  color: var(--success);
}

.quiz-result.error {
  background: var(--error-bg);
  border: 1px solid var(--error);
  color: var(--error);
}

.quiz-result.info {
  background: var(--info-bg);
  border: 1px solid var(--info);
  color: var(--info);
}

/* ================= РЕЗУЛЬТАТЫ УРОКА ================= */
.lesson-summary {
  text-align: center;
  padding: 2rem;
}

.lesson-summary .score {
  font-size: 3rem;
  font-weight: 700;
  background: var(--accent-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  margin: 1rem 0;
}

.lesson-summary .score-label {
  color: var(--text-secondary);
  font-size: 1.1rem;
  margin-bottom: 1.5rem;
}

.summary-stats {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1rem;
  margin: 2rem 0;
}

.stat-item {
  background: var(--secondary-bg);
  padding: 1rem;
  border-radius: 10px;
  border: 1px solid var(--border-color);
}

.stat-value {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--text-primary);
}

.stat-label {
  font-size: 0.85rem;
  color: var(--text-muted);
}

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

.trainer-panel {
  animation: fadeInUp 0.4s ease forwards;
}

/* ================= МОБИЛЬНАЯ АДАПТАЦИЯ ================= */
@media (max-width: 1024px) {
  .trainer-grid {
    grid-template-columns: 1fr;
    gap: 1.5rem;
  }
  
  .summary-stats {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (max-width: 768px) {
  .container {
    padding: 0 1rem;
  }
  
  .trainer-topbar .container {
    flex-direction: column;
    align-items: stretch;
    gap: 1rem;
  }
  
  .trainer-actions {
    justify-content: center;
  }
  
  .btn-trainer {
    flex: 1;
    min-width: 0;
    justify-content: center;
  }
  
  .trainer-title {
    text-align: center;
    justify-content: center;
  }
  
  .trainer-panel {
    padding: 1.25rem;
  }
  
  .trainer-panel h2 {
    font-size: 1.4rem;
  }
  
  .lesson-pagination {
    flex-direction: column;
    gap: 1rem;
    align-items: stretch;
  }
  
  .btn-pagination {
    width: 100%;
    min-width: 0;
  }
  
  .progress-container {
    justify-content: center;
  }
  
  .lessons-list {
    justify-content: center;
  }
  
  .quiz-header {
    flex-direction: column;
    align-items: flex-start;
    gap: 0.75rem;
  }
  
  .quiz-actions {
    flex-direction: column;
  }
  
  .btn-check,
  .btn-next {
    width: 100%;
    justify-content: center;
  }
  
  .summary-stats {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 480px) {
  .trainer-title {
    font-size: 1.1rem;
  }
  
  .lesson-link {
    padding: 0.5rem 0.75rem;
    font-size: 0.85rem;
    min-width: 45px;
  }
  
  .option-item {
    padding: 0.85rem 1rem;
  }
  
  .option-text {
    font-size: 0.95rem;
  }
}

/* ================= УТИЛИТЫ ================= */
.hidden {
  display: none !important;
}

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

.mt-1 { margin-top: 0.5rem; }
.mt-2 { margin-top: 1rem; }
.mt-3 { margin-top: 1.5rem; }
.mt-4 { margin-top: 2rem; }

.mb-1 { margin-bottom: 0.5rem; }
.mb-2 { margin-bottom: 1rem; }
.mb-3 { margin-bottom: 1.5rem; }
.mb-4 { margin-bottom: 2rem; }

/* Скроллбар — красный акцент */
::-webkit-scrollbar {
  width: 8px;
  height: 8px;
}

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

::-webkit-scrollbar-thumb {
  background: var(--border-color);
  border-radius: 4px;
}

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