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

.calculator {
  background: #fff;
  padding: 20px;
  border-radius: 15px;
  box-shadow: 0 0 20px black;
  width: 280px;
}

#display {
  width: 100%;
  height: 50px;
  font-size: 22px;
  margin-bottom: 10px;
  text-align: right;
  padding-right: 10px;
}

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

button {
  height: 50px;
  font-size: 18px;
  border: none;
  border-radius: 10px;
  cursor: pointer;
}

button:hover {
  background: #ddd;
}
.dark-btn {
  position: absolute;
  top: 20px;
  right: 20px;
  padding: 8px 15px;
  border-radius: 8px;
  cursor: pointer;
}

.dark body {
  background: black;
}

.dark .calculator {
  background: #222;
  color: white;
}

.dark button {
  background: #444;
  color: white;
}