/* Modern Calculator Styling */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
  background: linear-gradient(135deg, #1d2b64, #f8cdda);
  font-family: "Segoe UI", sans-serif;
}

.calculator {
  background: #222;
  padding: 20px;
  border-radius: 20px;
  box-shadow: 0 10px 20px rgba(0,0,0,0.3);
  width: 320px;
}

#display {
  width: 100%;
  height: 60px;
  font-size: 2rem;
  margin-bottom: 20px;
  border: none;
  outline: none;
  text-align: right;
  padding: 10px;
  border-radius: 10px;
  background: #333;
  color: #fff;
}

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

.btn {
  height: 60px;
  font-size: 1.5rem;
  border: none;
  border-radius: 15px;
  cursor: pointer;
  transition: 0.2s;
  background: #444;
  color: #fff;
}

.btn:hover {
  background: #555;
}

.operator {
  background: #ff9500;
  color: #fff;
}

.operator:hover {
  background: #e08900;
}

.equal {
  grid-column: span 2;
  background: #34c759;
  color: #fff;
}

.equal:hover {
  background: #28a745;
}

.zero {
  grid-column: span 2;
}