That is true, but offline there is a lot less incentive to cheat since you can't compare yourself to other players.
If there is a way to get ahead online, people will use that, it's not about the game, it's about being the best.
Offline, of course it is possible to cheat, but the only one who is affected is the cheater, so the player will be less inclined to cheat.
It would be cool if the players were able to influence the world and change the riddles or make their own, then you have a cool game going!