body {
  margin: 0;
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  background-color: #0c4987;
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
}

.calculator {
  background: rgb(148, 77, 14);
  padding: 2rem;
  border-radius: 20px;
  box-shadow: 0 10px 25px rgba(0, 0, 0, 0.1);
  width: 300px;
}

.display {
  height: 60px;
  background: #111827;
  color: #f9fafb;
  text-align: right;
  font-size: 2rem;
  padding: 0.5rem;
  border-radius: 10px;
  margin-bottom: 1rem;
}

.buttons {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 10px;
}

.btn {
  padding: 1rem;
  font-size: 1.25rem;
  background-color: #b7c8e9;
  border: none;
  border-radius: 10px;
  cursor: pointer;
  transition: background 0.2s;
}

.btn:hover {
  background-color: gold;
}

.equal {
  grid-column: span 2;
  background-color: silver;
  color: white;
}

.equal:hover {
  background-color: #2563eb;
}