body {
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
  background: #00000094;
  font-family: Arial, sans-serif;
}

.calculator {
  width: 320px;
  background: #fff;
  border-radius: 15px;
  box-shadow: 0px 4px 10px rgba(0,0,0,0.2);
  padding: 20px;
}

#display {
  width: 100%;
  height: 60px;
  font-size: 1.8rem;
  margin-bottom: 20px;
  text-align: right;
  padding: 10px;
  border: none;
  border-radius: 10px;
  background: #eee;
  box-sizing: border-box;
  overflow-x: auto;
}

.buttons {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 15px;
  justify-items: center;
}

.btn {
  height: 60px;
  width: 60px;
  font-size: 1.2rem;
  border: none;
  border-radius: 50%;
  background: #ddd;
  cursor: pointer;
  transition: background 0.2s ease;
  display: flex;
  justify-content: center;
  align-items: center;
}

.btn:hover {
  background: #bbb;
}

.operator {
  background: #f9a825;
  color: #fff;
}

.operator:hover {
  background: #f57f17;
}

.equal {
  background: #43a047;
  color: white;
}

.equal:hover {
  background: #2e7d32;
}

.clear {
  background: #e53935;
  color: white;
  border-radius: 30px;
  width: 100%;
  grid-column: span 2;
}

.clear:hover {
  background: #c62828;
}

.delete {
  background: #1e88e5;
  color: white;
  border-radius: 30px;
  width: 100%;
  grid-column: span 2;
}

.delete:hover {
  background: #1565c0;
}