I have some ideas about making a solitaire card game based on time travel in some way.

My core idea is that you have several columns of cards, with the columns representing the timeline (past on the left, future on the right).
You then fight battles in each column (against an automated opponent who just draws cards from a pile and puts them in the column)

Winning the fight means the timeline is saved, losing means a paradox occurs, which alters the timeline around that column