body {
  margin: 0;
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
  background: linear-gradient(to right, #6a11cb, #2575fc);
  font-family: "Arial", sans-serif;
}

.calculator {
  width: 340px;
  border-radius: 20px;
  box-shadow: 0 4px 20px rgba(0, 0, 0, 0.2);
  background: #333;
  overflow: hidden;
}

.display {
  background-color: #444;
  color: #fff;
  padding: 20px;
  font-size: 28px;
  text-align: right;
  border-bottom: 1px solid #555;
}

.buttons {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 12px;
  padding: 20px;
}

button {
  background-color: #555;
  border: none;
  border-radius: 50%;
  font-size: 20px;
  color: #fff;
  padding: 20px;
  cursor: pointer;
  transition: background-color 0.3s, transform 0.2s;
  outline: none;
}

button:active {
  transform: scale(0.95);
  background-color: #777;
}

button.zero {
  grid-column: span 2;
  border-radius: 50px;
}

button[data-value="/"],
button[data-value="*"],
button[data-value="-"],
button[data-value="+"],
button[data-value="="] {
  background-color: #4a90e2;
}

button[data-value="AC"],
button[data-value="+/-"],
button[data-value="%"] {
  background-color: #444;
}