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

body {
  font-family: 'Noto Sans', sans-serif;
  background: #000;
  color: #fff;
  overflow: hidden;
  height: 100vh;
}

#app {
  height: 100vh;
  display: flex;
  flex-direction: column;
}

.header {
  padding: 16px 20px;
  border-bottom: 1px solid #333;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.level-badge {
  font-size: 15px;
  font-weight: 600;
}

.knowledge-display {
  font-size: 13px;
  color: #888;
}

.back-btn {
  background: none;
  border: none;
  color: #fff;
  font-size: 15px;
  cursor: pointer;
  padding: 4px 8px;
}

.lesson-progress {
  font-size: 13px;
  color: #888;
}

.main {
  flex: 1;
  overflow-y: auto;
  padding: 20px;
}

.menu-view {
  display: flex;
  flex-direction: column;
  gap: 24px;
}

.progress-section {
  background: #1a1a1a;
  border-radius: 12px;
  padding: 20px;
}

.progress-info {
  display: flex;
  justify-content: space-between;
  margin-bottom: 12px;
  font-size: 13px;
}

.progress-info span:first-child {
  font-weight: 600;
}

.progress-info span:last-child {
  color: #888;
}

.progress-bar {
  height: 8px;
  background: #333;
  border-radius: 4px;
  overflow: hidden;
}

.progress-fill {
  height: 100%;
  background: #fff;
  transition: width 0.5s ease;
}

.stats-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
}

.stat-card {
  background: #1a1a1a;
  border-radius: 12px;
  padding: 20px;
  text-align: center;
}

.stat-value {
  font-size: 32px;
  font-weight: 700;
  margin-bottom: 4px;
}

.stat-label {
  font-size: 13px;
  color: #888;
}

.lessons-grid {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.lesson-card {
  background: #1a1a1a;
  border: 1px solid #333;
  border-radius: 12px;
  padding: 16px;
  cursor: pointer;
  transition: all 0.2s;
}

.lesson-card:active {
  transform: scale(0.98);
  background: #2a2a2a;
}

.lesson-card.locked {
  opacity: 0.5;
  cursor: not-allowed;
}

.lesson-card.locked:active {
  transform: none;
  background: #1a1a1a;
}

.lesson-card.completed {
  border-color: #4a4a4a;
}

.lesson-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 8px;
}

.lesson-title {
  font-weight: 600;
  font-size: 16px;
}

.completed-badge {
  background: #fff;
  color: #000;
  width: 24px;
  height: 24px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 14px;
  font-weight: 700;
}

.lesson-description {
  font-size: 14px;
  color: #888;
  margin-bottom: 12px;
}

.lesson-meta {
  display: flex;
  gap: 16px;
  font-size: 13px;
}

.lesson-duration {
  color: #888;
}

.lesson-knowledge {
  color: #fff;
  font-weight: 600;
}

.lesson-lock {
  margin-top: 8px;
  font-size: 12px;
  color: #666;
}

.lesson-view {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 40px 20px;
}

.lesson-content {
  max-width: 500px;
  width: 100%;
}

.lesson-content h2 {
  font-size: 24px;
  margin-bottom: 20px;
}

.content-progress {
  margin-bottom: 24px;
}

.content-progress-bar {
  height: 4px;
  background: #333;
  border-radius: 2px;
  overflow: hidden;
}

.content-progress-fill {
  height: 100%;
  background: #fff;
  transition: width 0.3s ease;
}

.content-text {
  font-size: 16px;
  line-height: 1.8;
  margin-bottom: 32px;
  color: #ccc;
}

.next-btn, .primary-btn {
  width: 100%;
  padding: 16px;
  background: #fff;
  border: none;
  border-radius: 12px;
  color: #000;
  font-size: 16px;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s;
}

.next-btn:active, .primary-btn:active {
  transform: scale(0.98);
}

.quiz-question {
  font-size: 18px;
  margin-bottom: 24px;
  line-height: 1.6;
}

.quiz-options {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.quiz-option {
  padding: 16px;
  background: #1a1a1a;
  border: 2px solid #333;
  border-radius: 12px;
  color: #fff;
  font-size: 15px;
  cursor: pointer;
  transition: all 0.2s;
  text-align: left;
}

.quiz-option:active {
  transform: scale(0.98);
}

.quiz-option.correct {
  border-color: #4caf50;
  background: #1a3a1a;
}

.quiz-option.incorrect {
  border-color: #f44336;
  background: #3a1a1a;
}

.quiz-option:disabled {
  cursor: not-allowed;
}

.completion-card {
  text-align: center;
  max-width: 400px;
}

.completion-icon {
  font-size: 64px;
  margin-bottom: 16px;
}

.completion-card h2 {
  font-size: 28px;
  margin-bottom: 16px;
}

.knowledge-gained {
  font-size: 20px;
  color: #4caf50;
  margin-bottom: 16px;
  font-weight: 600;
}

.level-info {
  font-size: 18px;
  margin-bottom: 32px;
  color: #888;
}