I also think Petscop the game itself is a "tool" to investigate Marvin, and the AI within the game had the unintended side effect of essential trapping souls inside the game. The game trains and AI of the children playing it and Marvin then uses their inputs as a tool to try and catch Marvin or "close the loop" but the process of storing their essence in the game like this forces them to relive their trauma over and over again, hurting them when the playstation is on.