style.css

body {
  background-color: #1a1c1f;
  color: white;
  background-color: black;
}

.calculator {
  max-width: 400px;
  margin: 20px auto 0 auto;
  padding: 20px;
  background-color: #2b2f34;
  border-radius: 10px;
}

.display {
  height: 70px;
  background-color: #333;
  margin-bottom: 10px;
  border-radius: 5px;
  display: flex;
  align-items: center;
  justify-content: flex-end;
  padding-right: 20px;
  font-size: 2rem;
  color: #fff;
}

.btn {
  background-color: #3a3d41;
  border: none;
  color: white;
  font-size: 1.5rem;
  border-radius: 10px;
  padding: 15px 0;
  transition: background-color 0.3s;
}

.btn:hover {
  background-color: #5a5d61;
}

.btn-ac {
  background-color: #75529f;
}

.btn-equal {
  background-color: #1e5867;
}

.btn-operator {
  background-color: #4a4e53;
}

.row {
  margin-bottom: 10px;
}