Cultist Simulator is a rather interesting game. In fact, it is actually a rather interesting review to try to write since to tell you how to play the game in itself would actually mess up a huge part of the game. The game is a card game, you use the card to make choices. Each card is used to do a different thing such as go to work or study. You will need to manage your money, health, and even your mental health, or your dread. Yes, you can go insane and die. You can die in a whole host of ways actually, then pick up as a new character. Once I died and restarted as a detective that had a file on my last character.
This all seems pretty vague, and the reason it sounds vague is telling you too much would actually ruin the game. The idea of the game is mostly figuring out how and what to do and what happens when you do it. I have included a video so you can see it in action, but I suggest just trying it for yourself. Best wishes and may the gaming gods bring you glory.