body {
  font-family: Arial, sans-serif;
  background: #f0f0f0;
  text-align: center;
  padding-top: 40px;
}

.container {
  display: inline-block;
  background: #fff;
  border: 2px solid #ccc;
  border-radius: 10px;
  padding: 20px;
}

.result {
  margin-bottom: 20px;
}

#display {
  font-size: 2em;
  padding: 10px;
  border: 1px solid #aaa;
  border-radius: 5px;
  background: #eaeaea;
  text-align: right;
  min-width: 250px;
  height: 40px;
  overflow-x: auto;
}

.buttons {
  display: grid;
  grid-template-columns: repeat(4, 60px);
  gap: 10px;
}

button {
  font-size: 1.2em;
  padding: 10px;
  border: none;
  border-radius: 8px;
  background: #26a69a;
  color: white;
  cursor: pointer;
  transition: background 0.2s;
}

button:hover {
  background: #00796b;
}