body {
  background: url("https://img.freepik.com/premium-vector/calculator-pencils-background_188544-6127.jpg");
  background-size: cover;
  font-family: Arial, sans-serif;
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
  margin: 0;
}

.calculator {
  background: #eea245;
  padding: 20px;
  border-radius: 16px;
  box-shadow: 0 8px 20px #cbd5e0;
  width: 280px;
}

#display {
  background: #222;
  color: #fff;
  font-size: 2rem;
  font-weight: bolder;
  padding: 15px;
  border-radius: 8px;
  text-align: right;
  margin-bottom: 20px;
}

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

button {
  padding: 20px;
  font-size: 1.2rem;
  font-weight: bolder;
  border: none;
  border-radius: 8px;
  background: #e2e8f0;
  cursor: pointer;
  transition: background 0.2s;
}

button:hover {
  background: #5e48db9a;
}

.c {
  grid-column: span 2;
}

.zero {
  grid-column: span 2;
}