body {
  font-family: Arial, sans-serif;
  background-color: #f0f0f0;
}

.container {
  text-align: center;
  margin-top: 100px;
}

#color-box {
  width: 400px;
  height: 300px;
  background-color: #3498db;
  margin: 20px auto;
  border-radius: 8px;
  transition: background-color 0.3s ease;
}

#change-color-btn {
  padding: 10px 20px;
  font-size: 16px;
  background-color: #2ecc71;
  color: white;
  border: none;
  border-radius: 5px;
  cursor: pointer;
}

#change-color-btn:hover {
  background-color: #27ae60;
  transition: 0.5s;
}