body {
  background-color: #2c2c2c;
  color: white;
  font-family: Arial, sans-serif;
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
  margin: 0;
}

.calculator {
  background-color: #1e1e1e;
  border-radius: 12px;
  overflow: hidden;
  width: 320px;
  box-shadow: 0 4px 20px rgba(0, 0, 0, 0.5);
  display: flex;
  flex-direction: column;
}

.display {
  background-color: #000;
  color: #0f0;
  font-size: 2.5rem;
  padding: 20px;
  text-align: right;
  overflow-x: auto;
}

.buttons {
  display: flex;
  flex-wrap: wrap;
}

.btn {
  flex: 1 0 25%;
  padding: 20px;
  font-size: 1.4rem;
  border: 1px solid #444;
  background-color: #333;
  color: white;
  cursor: pointer;
  outline: none;
}

.btn:hover {
  background-color: #555;
}

.function {
  background-color: #555;
}

.operator {
  background-color: #ff9500;
}

.operator:hover {
  background-color: #e68900;
}

.equals {
  background-color: #28a745;
  flex: 1 0 25%;
}

.equals:hover {
  background-color: #218838;
}

.zero {
  flex: 1 0 50%;
}