body {
  background: linear-gradient(135deg, #667eea, #764ba2);
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
  font-family: Arial;
}

.calculator {
  background: #1e1e2f;
  padding: 20px;
  border-radius: 20px;
  width: 300px;
  box-shadow: 0 10px 30px rgba(0,0,0,0.4);
}

#display {
  width: 100%;
  height: 60px;
  font-size: 24px;
  margin-bottom: 15px;
  text-align: right;
  padding: 10px;
  border-radius: 10px;
  border: none;
  background: #2c2c3e;
  color: white;
}

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

button {
  padding: 15px;
  font-size: 18px;
  border: none;
  border-radius: 10px;
  cursor: pointer;
  background: #3a3a55;
  color: white;
  transition: 0.2s;
}

button:hover {
  background: #50507a;
}

.equal {
  background: #4CAF50;
}

.equal:hover {
  background: #45a049;
}

.clear {
  background: #e74c3c;
}

.zero {
  grid-column: span 2;
}