body {
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
  background-color: #222;
  font-family: Arial, sans-serif;
}

#calculadora {
  background: #333;
  padding: 20px;
  border-radius: 10px;
  box-shadow: 0px 4px 10px rgba(0, 0, 0, 0.3);
  width: 260px;
  text-align: center;
}


#display {
  width: 100%;
  height: 50px;
  font-size: 2em;
  text-align: right;
  padding: 10px;
  border: none;
  outline: none;
  background: #000;
  color: #fff;
  margin-bottom: 10px;
  border-radius: 5px;
}


#teclado {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 5px;
}

button {
  width: 60px;
  height: 60px;
  font-size: 1.5em;
  border: none;
  cursor: pointer;
  background: #444;
  color: #fff;
  border-radius: 5px;
  transition: 0.3s;
}


button:hover {
  background: #555;
}

button:active {
  background: #777;
}

button.zero {
  grid-column: span 2;
  width: 100%;
}

button:nth-child(4n),
button:last-child {
  background: #ff9800;
}

button:nth-child(4n):hover,
button:last-child:hover {
  background: #e68900;
}