body {
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh; 
  font-family: Arial, sans-serif;
}

.calculator {
  background: #222;
  padding: 20px;
  border-radius: 12px;
  width: 300px;
}

#display {
  width: 100%;
  height: 60px;
  font-size: 26px;
  text-align: right;
  padding: 10px;
  border-radius: 8px;
  border: none;
  margin-bottom: 15px;
  color: white;
}

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

button {
  height: 55px;
  font-size: 18px;
  border: none;
  border-radius: 8px;
  cursor: pointer;
  background: #333;
  color: rgb(255, 255, 255);
  transition: 0.3s;
}

button:hover {
  background: #7e7b7b;
}

.zero {
  grid-column: span 2;
}

button:nth-child(4n) {
  background: #ff9500;
}

button:nth-child(4n):hover {
  background: #ffa733;
}