The "game" is done with the Web Speech API: The Web Speech API allows you to embed speech data in web applications. The Web Speech API has two parts: SpeechSynthesis (Text-to-Speech) and SpeechRecognition (asynchronous speech recognition). https://developer.mozilla.org/en-US/docs/Web/API/Web_Speech_API
This project is part of one of Alura's front-end courses.