body {
  background-color: #f5f5f5;
  font-family: sans-serif;
  text-align: center;
  margin-top: 100px;
}

.container {
  background: white;
  display: inline-block;
  padding: 40px;
  border-radius: 12px;
  box-shadow: 0 0 15px rgba(0,0,0,0.2);
}

button {
  padding: 10px 20px;
  font-size: 18px;
  cursor: pointer;
}

#result {
  font-size: 24px;
  margin-top: 20px;
}