body {
  margin: 0;
  padding: 0;
  background-color: #f0f0f0;
}

.calculator {
  margin: 50px auto;
  padding: 20px;
  background-color: #fff;
  border-radius: 10px;
  box-shadow: 0 0 10px rgba(0, 0, 0, 0.2);
  width: 300px;
}

.display {
  margin-bottom: 10px;
}

.display input {
  width: 100%;
  padding: 10px;
  font-size: 24px;
  text-align: right;
  box-sizing: border-box;
  border: none;
  border-radius: 5px;
  background-color: #f8f8f8;
}

.buttons button {
  width: 50px;
  height: 50px;
  margin: 5px;
  padding: 10px;
  font-size: 24px;
  color: #fff;
  background-color: #333;
  border: none;
  border-radius: 5px;
  cursor: pointer;
}

.buttons button:hover {
  background-color: #555;
}

.operator {
  background-color: #ff9900;
}

.operator:hover {
  background-color: #ffbf40;
}

.number {
  background-color: #66cc66;
}

.number:hover {
  background-color: #99d699;
}

.zero {
  width: 110px;
}

.equal {
  background-color: #66ccff;
}

.equal:hover {
  background-color: #99d6ff;
}