* {
  box-sizing: border-box;
  font-family: Arial, sans-serif;
}

body {
  height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
  background: #1e1e1e;
}

.calc {
  width: 260px;
  background: #2a2a2a;
  padding: 15px;
  border-radius: 12px;
}

#display {
  width: 100%;
  height: 50px;
  margin-bottom: 10px;
  font-size: 24px;
  text-align: right;
  padding: 10px;
  border: none;
  border-radius: 8px;
  background: #111;
  color: #fff;
}

.buttons {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 8px;
}

button {
  height: 45px;
  font-size: 18px;
  border: none;
  border-radius: 8px;
  background: #3a3a3a;
  color: #fff;
  cursor: pointer;
}

button:hover {
  background: #505050;
}

.equal {
  grid-row: span 2;
  background: #ff9500;
}

.equal:hover {
  background: #e08900;
}

.zero {
  grid-column: span 2;
}