* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  height: 100%;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", system-ui, sans-serif;
  background: linear-gradient(135deg, #4a90e2 0%, #7b68ee 100%);
  color: #fff;
  -webkit-tap-highlight-color: transparent;
}

#app {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 1.5rem;
}

.screen {
  width: 100%;
  max-width: 520px;
  text-align: center;
}

h1 {
  font-size: 2.5rem;
  margin: 0 0 0.5rem;
}

.subtitle {
  font-size: 1.1rem;
  opacity: 0.85;
  margin: 0 0 2rem;
}

input[type="text"],
input[type="number"] {
  width: 100%;
  font-size: 1.5rem;
  padding: 0.8rem 1rem;
  border: none;
  border-radius: 12px;
  background: rgba(255, 255, 255, 0.95);
  color: #222;
  text-align: center;
  margin-bottom: 1rem;
  outline: none;
}

input[type="number"] {
  font-size: 2.2rem;
  font-weight: 700;
}

input:focus {
  box-shadow: 0 0 0 3px rgba(255, 255, 255, 0.5);
}

.big-btn {
  width: 100%;
  font-size: 1.4rem;
  font-weight: 700;
  padding: 0.9rem 1rem;
  border: none;
  border-radius: 12px;
  background: #fff;
  color: #4a90e2;
  cursor: pointer;
  transition: transform 0.05s ease;
}

.big-btn:active {
  transform: scale(0.97);
}

.quiz-header {
  display: flex;
  justify-content: space-between;
  font-size: 1.1rem;
  font-weight: 600;
  opacity: 0.9;
  margin-bottom: 2rem;
}

.question {
  font-size: 5rem;
  font-weight: 800;
  margin: 1rem 0 2rem;
  letter-spacing: 0.05em;
}

.feedback {
  margin-top: 1.5rem;
  padding: 1rem;
  border-radius: 12px;
  font-size: 1.5rem;
  font-weight: 700;
}

.feedback.correct {
  background: rgba(76, 217, 100, 0.95);
  color: #fff;
}

.feedback.wrong {
  background: rgba(255, 80, 80, 0.95);
  color: #fff;
}

.summary {
  font-size: 1.3rem;
  line-height: 1.8;
  background: rgba(255, 255, 255, 0.15);
  padding: 1.5rem;
  border-radius: 16px;
  margin-bottom: 2rem;
}

.summary strong {
  font-size: 1.6rem;
}