Essentially, every [x] hours/minutes/seconds, display a prompt that requires the user to press a random key (A-Z, or whatever). I would assume the prompt would be similar the AFK screen, having a timeout and all. Upon pressing the input, allow the user to return to playing. Otherwise, if the input isn’t sent within the given time, kick the user off the machine.
I think you can read minds, because that was literally my suggestion to the team, only mine was if the button was incorrect, it would keep shuffling the key that you had to press (just so if you hit the wrong one on accident you wouldn’t be punished for it).
We’re still working on a solution for this issue however.
I would personally make it so that it sounds to them like some good shit is happening, but in reality they’re losing all of their money. Like on blackjack it would make winning sounds frequently, but actually always start you over 21.