So mtgox could have been implemented in Magic: The Gathering.
(MTGox was a trading site for virtual trading cards, not real ones. It was "MTG Online: Exchange", not "MTG: Online Exchange"...)
>The model of the tape is as follows. A series of Zombie tokens controlled by Alex represent the tape to the right of the current head
However, it seems that there is a limit to the number of creature tokens in MTGO which does not exist in the paper game.
You're only allowed to say MTGO is not Turing complete if you also agree that Java is not Turing complete (because the 32-bit JVM has bounded memory it can access).
https://www.youtube.com/watch?v=AGXG5rNe_tI
For those who are confused, the card involved there is Oblivion Ring:
http://gatherer.wizards.com/Pages/Card/Details.aspx?multiver...
Its effect is that, when it comes into play, you choose a non-land card in play that gets exiled (removed from play) for as long as Oblivion Ring stays in play, then gets returned once Oblivion Ring leaves play. This game devolves into a situation where there are three Oblivion Rings and no other non-land cards, so: Ring 1 exiles Ring 2, which returns Ring 3, which exiles Ring 1, which returns Ring 2, which exiles Ring 3, which returns Ring 1, which exiles Ring 2, and so on to infinity. The rules state that when a loop like this occurs (which is not often in real play), the game is an automatic draw.