body {
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
  font-family: "Open Sans", sans-serif;
  background: linear-gradient(135deg, #e6e9f0, #eef1f5);
}

.calculator {
  width: 250px;
  background-color: #fff;
  border-radius: 8px;
  box-shadow: 0 0 10px (rgb(0, 0, 0.1));
  padding: 20px;
}

#display {
  width: 230px;
  height: 50px;
  margin-bottom: 20px;
  font-size: 24px;
  text-align: right;
  padding: 10px;
  border: 1px solid #ddd;
  border-radius: 5px;
}

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

.btn {
  padding: 15px;
  margin-right: 2px;
  margin-bottom: 5px;
  border: none;
  border-radius: 5px;
  background-color: #f0f0f5;
  cursor: pointer;
  transition: background-color 0.2s, transform 0.1s;
}

.btn:active {
  background-color: #ddd;
}

.operator {
  background-color: #f9a825;
}

.operator:active {
  background-color: #e53935;
}

.clear {
  grid-column: span 4;
  background-color: #e53935;
  color: white;
  width: 100%;
}

.clear:active {
  background-color: #c62828;
}