body {
  margin: 0;
  padding: 0;
  font-family: "Segoe UI", sans-serif;
  background-color: #282c34;
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
}

.calculator {
  background-color: #1e1e1e;
  border-radius: 20px;
  box-shadow: 0 10px 25px rgba(0, 0, 0, 0.3);
  overflow: hidden;
  width: 320px;
}

.display {
  background-color: #111;
  color: #0f0;
  font-size: 2.5rem;
  padding: 20px;
  text-align: right;
  height: 80px;
  box-sizing: border-box;
  overflow-x: auto;
}

.buttons {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  grid-gap: 1px;
  background-color: #444;
}

.btn {
  padding: 20px;
  font-size: 1.5rem;
  background-color: #333;
  color: white;
  border: none;
  outline: none;
  cursor: pointer;
  transition: background-color 0.2s;
}

.btn:hover {
  background-color: #555;
}

.operator {
  background-color: #ff8c00;
  color: #000;
}

.operator:hover {
  background-color: #ffa500;
}

.clear {
  background-color: #ff3b30;
}

.clear:hover {
  background-color: #ff5e57;
}

.equals {
  background-color: #4cd964;
  grid-row: span 2;
}

.equals:hover {
  background-color: #66e27f;
}

.zero {
  grid-column: span 2;
}