It would be possible for a student to remix a game from the public projects. I don’t think there’s any way for you to tell for sure that they have done this, unfortunately.
The public projects can be seen here:
I have had this happen before and I was able to address it by asking the student to explain the code to me. Of course that was when we were in a classroom together and I was able to do it in a non-threatening way. The student admitted they had copied some of the code and I was able to help them come up with their own idea.
In this situation, I may ask the student if they had collaborated with another student as their project was very similar to the project of another student and see what they say.
Here’s a previous thread on this related situation.
I’d love to hear from others on successful approaches to combatting this.
Mike