body {
  font-family: 'Segoe UI', Arial, sans-serif;
  background: linear-gradient(135deg, #e0e7ff 0%, #f5f5f5 100%);
  min-height: 100vh;
  margin: 0;
  display: flex;
  flex-direction: column;
  align-items: center;
}
.back-button {
  display: inline-block;
  margin: 2rem 0 1rem 0;
  padding: 0.5rem 1.2rem;
  background: #f3f6fd;
  color: #2a4d8f;
  border-radius: 2rem;
  text-decoration: none;
  font-weight: 600;
  font-size: 1rem;
  box-shadow: 0 1px 6px rgba(80, 112, 255, 0.08);
  transition: background 0.18s, color 0.18s, box-shadow 0.18s;
  border: 1px solid #e0e7ff;
}
.back-button:hover, .back-button:focus {
  background: #4f8cff;
  color: #fff;
  box-shadow: 0 2px 12px rgba(80, 112, 255, 0.14);
}
.challenge-question {
  background: #fff;
  border-radius: 1rem;
  box-shadow: 0 2px 12px rgba(80, 112, 255, 0.10);
  margin-bottom: 1.5rem;
  padding: 1.2rem 2rem;
  max-width: 420px;
  width: 100%;
  text-align: center;
}
.challenge-question h1 {
  font-size: 1.3rem;
  color: #2a4d8f;
  margin: 0 0 0.5rem 0;
  font-weight: 700;
}
.navbar {
  display: flex;
  gap: 20px;
  background: #222;
  padding: 10px 20px;
  border-radius: 0.8rem;
  box-shadow: 0 2px 8px rgba(80, 112, 255, 0.10);
  margin-bottom: 2rem;
  flex-wrap: wrap;
}
.navbar a {
  color: #fff;
  text-decoration: none;
  padding: 8px 12px;
  transition: background 0.3s, color 0.3s;
  border-radius: 0.5rem;
  font-weight: 500;
  font-size: 1rem;
}
.navbar a:hover,
.navbar a.active,
.navbar a:focus-visible {
  background: #fff;
  color: #222;
}
@media (max-width: 500px) {
  .challenge-question {
    padding: 0.8rem 0.5rem;
    max-width: 98vw;
    font-size: 0.97rem;
  }
  .navbar {
    padding: 8px 2vw;
    gap: 10px;
    max-width: 98vw;
  }
  .navbar a {
    font-size: 0.95rem;
    padding: 7px 8px;
  }
}