Are you looking to get some time travel in your role-playing game? Let me tell you why that's a terrible idea, but also why it's an awesome idea. Why is Back to the Future a terrible model for time travel, but on the other hand, why is it great? What's up with the Novikov self-consistency principle? Can you break a time loop? Should you break a time loop? How do you even begin to handle all this nonsense in an RPG setting where the whole point is that you don't know what the players are actually going to do?
Why listen to me, you ask? I wrote a video game called Quantum Break, and in order to do that, I had to spend, no joke, five years thinking about time travel logic. Please, let me share my pain.