body {
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
  background-color: #f4f4f4;
}

.calculator {
  width: 250px;
  background: white;
  padding: 20px;
  border-radius: 10px;
  box-shadow: 0px 0px 10px rgba(0, 0, 0, 0.1);
}

#display {
  width: 100%;
  height: 50px;
  text-align: right;
  font-size: 1.5em;
  margin-bottom: 10px;
  padding: 10px 15px;
  border: 2px solid #ccc;
  background: #eee;
  box-sizing: border-box;
  border-radius: 5px;
}

.buttons {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 5px;
}

button {
  width: 100%;
  height: 50px;
  font-size: 1.2em;
  border: none;
  cursor: pointer;
  background: #ddd;
  border-radius: 5px;
}

button.operator {
  background: #f39c12;
  color: white;
}

button.equal {
  background: #2ecc71;
  color: white;
}

button.clear {
  background: #e74c3c;
  color: white;
}