body {
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
  background: #f4f4f4;
  font-family: Arial, sans-serif;
}

.calculator {
  background: #fff;
  padding: 20px;
  border-radius: 10px;
  box-shadow: 0px 4px 8px rgba(0,0,0,0.1);
}

input {
  width: 100%;
  height: 50px;
  margin-bottom: 10px;
  text-align: right;
  font-size: 20px;
}

button {
  width: 50px;
  height: 50px;
  margin: 5px;
  font-size: 18px;
  border: none;
  border-radius: 5px;
  background: #ddd;
  cursor: pointer;
}

button:hover {
  background: #bbb;
}