The assignments in this class ask you to make a "new game". What does that mean?
It means that you expect the experience of the game to be novel. In other words, if we picked a random, reasonably-game-savvy person and had them play your game, they would feel like they were playing something that they hadn't played or seen before.
I expect best-effort novelty. Make something you think is fresh. Spend a bit of effort to verify this (e.g., asking your room-mate). I'm not going to scour the internet looking for duplicates of your game. I am not going to mark your game down because, e.g., it happens to overlap with an obscure Ludum Dare submission.
One of the easiest ways to create a novel experience is to work from a known idea and change one crucial thing in the theme or gameplay. The "crucial" part of that statement is crucial. If the thing you change doesn't have a big impact on the game experience, then the game will not feel new.
Some concrete examples of games that used this strategy well: