Final big general test
It would be great if at the end of the course there was some final big general test, which contains questions for all levels of the course. This would consolidate the knowledge gained. Then you can issue a certificate.
It is even possible to add practical tasks, for example: create the correct registration form. And also add the game to the "arcade" section In which users who have completed the course will help check the assignments. (this is rather a dumb idea, but maybe you can develop it)