* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
}

body {
  background-color: #f3f4f6;
  color: #1f2937;
  display: flex;
  flex-direction: column;
  min-height: 100vh;
}

.app-header {
  background-color: #2563eb;
  color: white;
  padding: 16px;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.quiz-container {
  flex: 1;
  padding: 16px;
  max-width: 600px;
  margin: 0 auto;
  width: 100%;
}

#quiz-box, #result-box {
  background: white;
  padding: 20px;
  border-radius: 12px;
  box-shadow: 0 2px 8px rgba(0,0,0,0.08);
}

.options-group {
  margin: 20px 0;
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.option-btn {
  padding: 12px 16px;
  border: 1px solid #d1d5db;
  border-radius: 8px;
  background: white;
  text-align: left;
  font-size: 15px;
  cursor: pointer;
}

.option-btn.selected {
  background-color: #eff6ff;
  border-color: #2563eb;
  color: #2563eb;
  font-weight: bold;
}

.nav-buttons button, #result-box button {
  width: 100%;
  padding: 12px;
  background-color: #2563eb;
  color: white;
  border: none;
  border-radius: 8px;
  font-weight: bold;
  cursor: pointer;
}

.hidden { display: none; }