body {
  margin: 0;
  height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
  background: #2e2e2e;
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

.calculator {
  background: #1e1e1e;
  padding: 30px;
  border-radius: 20px;
  box-shadow: 0 8px 25px rgba(0, 0, 0, 0.6);
}

.display {
  background: #cdd19e;
  color: #333;
  font-size: 30px;
  padding: 20px;
  text-align: right;
  border-radius: 10px;
  margin-bottom: 20px;
  height: 60px;
  box-shadow: inset 0 0 5px rgba(0,0,0,0.5);
}

.buttons {
  display: grid;
  grid-template-columns: repeat(4, 60px);
  grid-gap: 15px;
  justify-content: center;
}

button {
  background: #2f2f2f;
  color: #fff;
  font-size: 20px;
  border: none;
  border-radius: 10px;
  height: 60px;
  width: 60px;
  box-shadow: 0 4px #1a1a1a;
  cursor: pointer;
  transition: transform 0.1s, background 0.2s;
}

button:active {
  transform: scale(0.95);
}

button:hover {
  background: #444;
}

.equals {
  background-color: #007bff;
  color: white;
}

.equals:hover {
  background-color: #0056b3;
}

.clear {
  background-color: #d32f2f;
  color: white;
}

.clear:hover {
  background-color: #b71c1c;
}