Create a native iOS app in Swift that utilizes Core Motion framework to recognize when the user has shaken their device. The app should respond to the shake gesture by triggering a customized action or animation. The app should also provide feedback to the user indicating that their gesture has been detected. The UI should be simple and intuitive, designed with a modern and engaging style. The app should be fully functional and tested on multiple devices to ensure robustness and reliability.
This prompt doesn't seem malicious.