* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto,
    "Helvetica Neue", Arial, sans-serif;
  background: linear-gradient(135deg, #1e3a8a, #7c3aed);
  color: #1f2937;
}

.card {
  background: #ffffff;
  padding: 2.5rem 3rem;
  border-radius: 16px;
  box-shadow: 0 20px 40px rgba(0, 0, 0, 0.25);
  max-width: 520px;
  width: 90%;
  text-align: center;
}

h1 {
  margin-top: 0;
  font-size: 1.9rem;
  color: #1e293b;
}

p {
  line-height: 1.6;
  color: #475569;
}

button {
  margin-top: 1rem;
  padding: 0.75rem 1.75rem;
  font-size: 1rem;
  font-weight: 600;
  color: #ffffff;
  background: #4f46e5;
  border: none;
  border-radius: 8px;
  cursor: pointer;
  transition: background 0.2s ease, transform 0.1s ease;
}

button:hover {
  background: #4338ca;
}

button:active {
  transform: scale(0.97);
}

.result {
  min-height: 1.5rem;
  margin-top: 1rem;
  font-weight: 600;
  color: #16a34a;
}