Corrected entry: At the end, when he's in the room where Halliday grew up, with the younger version of Halliday, Young Halliday is playing Yar's Revenge with what appears to be an Intellivision and Intellivision controller. Yar's Revenge was an Atari game.
zendaddy621
13th Aug 2018
Correction: Since Halliday created the Oasis, he could have altered any portion of it to his whims, especially a portion not accessible to just anyone, so it's not much of a stretch for him to have altered a tiny detail such as which games he was able to play on any given console; he could have chosen this particular setup for any number of reasons such as personal preference, aesthetics, nostalgia, etc.
zendaddy621
In addition, he may have just made an error due to age.
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