body {
  font-family: system-ui, sans-serif;
  background: #f9fafb;
  color: #1f2937;
  margin: 0;
  padding: 2rem;
}

.card {
  background: #ffffff;
  padding: 2rem;
  border-radius: 1rem;
  box-shadow: 0 10px 20px rgba(0, 0, 0, 0.05);
  max-width: 500px;
  margin: auto;
}

h1 {
  font-size: 1.75rem;
  margin-bottom: 1rem;
}

input {
  width: 100%;
  padding: 0.75rem;
  font-size: 1rem;
  border: 1px solid #d1d5db;
  border-radius: 0.5rem;
  margin-bottom: 0.5rem;
}

input.error {
  border-color: red;
}

button {
  background: #2563eb;
  color: white;
  border: none;
  border-radius: 0.5rem;
  padding: 0.75rem;
  font-size: 1rem;
  width: 100%;
  cursor: pointer;
}

button:hover {
  background: #1e40af;
}

#result {
  margin-top: 1.5rem;
  font-size: 1rem;
}

#hints {
  font-size: 0.85rem;
  color: #6b7280;
  margin-bottom: 1rem;
}

#hints code {
  background: #e5e7eb;
  padding: 0.1rem 0.3rem;
  border-radius: 4px;
}

#retryBtn {
  margin-top: 1rem;
  background: #f59e0b; /* amber-500 */
  color: white;
  border: none;
  padding: 0.5rem 1rem;
  border-radius: 0.375rem;
  font-weight: 600;
  cursor: pointer;
}

#retryBtn:hover {
  background: #d97706;
}