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

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  min-height: 100vh;
  color: #1a202c;
}

header {
  background: rgba(255, 255, 255, 0.95);
  padding: 40px 20px;
  text-align: center;
  box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
}

header h1 {
  font-size: clamp(28px, 5vw, 42px);
  color: #667eea;
  margin-bottom: 10px;
}

.subtitle {
  color: #718096;
  font-size: clamp(14px, 2vw, 18px);
}

main {
  max-width: 800px;
  margin: 0 auto;
  padding: 30px 20px;
}

section {
  background: rgba(255, 255, 255, 0.95);
  border-radius: 16px;
  padding: 24px;
  margin-bottom: 24px;
  box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
}

h2 {
  font-size: clamp(20px, 3vw, 24px);
  color: #2d3748;
  margin-bottom: 20px;
}

.topic-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
  gap: 12px;
}

.topic-btn {
  background: #f7fafc;
  border: 2px solid #e2e8f0;
  border-radius: 12px;
  padding: 16px;
  cursor: pointer;
  transition: all 0.2s;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
}

.topic-btn:hover {
  border-color: #667eea;
  background: #ebf4ff;
}

.topic-btn.active {
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  color: white;
  border-color: transparent;
}

.topic-btn .icon {
  font-size: 32px;
}

.word-list {
  display: grid;
  gap: 12px;
}

.word-card {
  background: #f7fafc;
  border-left: 4px solid #667eea;
  padding: 16px;
  border-radius: 8px;
  transition: transform 0.2s;
}

.word-card:hover {
  transform: translateX(8px);
}

.word-card .en {
  font-size: clamp(16px, 2vw, 20px);
  font-weight: 600;
  color: #2d3748;
  margin-bottom: 4px;
}

.word-card .ru {
  color: #718096;
  font-size: clamp(14px, 2vw, 16px);
}

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

.test-question {
  font-size: clamp(18px, 2.5vw, 24px);
  font-weight: 600;
  color: #2d3748;
  margin-bottom: 24px;
  min-height: 60px;
}

.test-options {
  display: grid;
  gap: 12px;
  margin-bottom: 20px;
}

.test-option {
  background: #f7fafc;
  border: 2px solid #e2e8f0;
  border-radius: 8px;
  padding: 16px;
  cursor: pointer;
  transition: all 0.2s;
  font-size: clamp(14px, 2vw, 16px);
}

.test-option:hover {
  border-color: #667eea;
  background: #ebf4ff;
}

.test-option.correct {
  background: #c6f6d5;
  border-color: #48bb78;
  color: #22543d;
}

.test-option.wrong {
  background: #fed7d7;
  border-color: #f56565;
  color: #742a2a;
}

.test-result {
  font-size: clamp(16px, 2vw, 18px);
  font-weight: 600;
  min-height: 24px;
  margin-bottom: 16px;
}

.test-btn {
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  color: white;
  border: none;
  border-radius: 8px;
  padding: 14px 32px;
  font-size: 16px;
  font-weight: 600;
  cursor: pointer;
  transition: transform 0.2s;
}

.test-btn:hover {
  transform: scale(1.05);
}

.test-btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
  transform: none;
}

.progress-stats {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 16px;
  margin-bottom: 20px;
}

.stat {
  background: #f7fafc;
  padding: 20px;
  border-radius: 12px;
  text-align: center;
}

.stat-value {
  display: block;
  font-size: clamp(24px, 4vw, 36px);
  font-weight: 700;
  color: #667eea;
  margin-bottom: 8px;
}

.stat-label {
  color: #718096;
  font-size: clamp(12px, 1.5vw, 14px);
}

.reset-btn {
  background: #fc8181;
  color: white;
  border: none;
  border-radius: 8px;
  padding: 12px 24px;
  font-size: 14px;
  cursor: pointer;
  width: 100%;
}

.reset-btn:hover {
  background: #f56565;
}

footer {
  text-align: center;
  padding: 20px;
  color: rgba(255, 255, 255, 0.8);
  font-size: 14px;
}

@media (max-width: 600px) {
  main {
    padding: 20px 16px;
  }
  
  section {
    padding: 20px 16px;
  }
  
  .progress-stats {
    grid-template-columns: 1fr;
  }
}