body {
  font-family: -apple-system, "Segoe UI", sans-serif;
  background: #0b1b33;
  color: #f0f4fa;
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 100vh;
  margin: 0;
}
.card {
  background: #142a4d;
  padding: 2rem 2.5rem;
  border-radius: 12px;
  min-width: 320px;
  box-shadow: 0 8px 24px rgba(0,0,0,0.3);
}
h1 { margin: 0 0 0.25rem; font-size: 1.4rem; }
.sub { color: #9db4d6; margin-bottom: 1.25rem; }
form { display: flex; flex-direction: column; gap: 0.5rem; }
input {
  padding: 0.6rem 0.75rem;
  border-radius: 6px;
  border: 1px solid #2a4a7a;
  background: #0b1b33;
  color: #f0f4fa;
}
button {
  padding: 0.6rem 0.75rem;
  border-radius: 6px;
  border: none;
  background: #3d7ef2;
  color: white;
  font-weight: 600;
  cursor: pointer;
}
.result { margin-top: 0.75rem; min-height: 1.2rem; }
.result.error { color: #ff8080; }
.hint { font-size: 0.85rem; color: #7d95bc; margin: 0 0 1rem; }
.hint code { background: #0b1b33; padding: 0.1rem 0.35rem; border-radius: 4px; }
pre {
  margin-top: 1rem;
  padding: 0.75rem;
  background: #0b1b33;
  border: 1px solid #2a4a7a;
  border-radius: 6px;
  font-size: 0.8rem;
  overflow-x: auto;
  white-space: pre-wrap;
  word-break: break-all;
  min-height: 1.5rem;
}