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Category: Retrogames

Retrogame Archaeology

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Atari Landfill Excavation

I am sure "Retrogame Archaeology" term sounds odd to you. It sounded strange to me in the first place too. But in science, a new field of research is emerging under this name. When you hear archeology, don't think of simply excavation of historical places. For instance, in 1983 Atari buried hundreds of thousands of games in Alamogordo, New Mexico and those games were discovered in 2014. This is not what they mean by "Retrogame Archeology".

In order to better understand "Retrogame Archeology", it is a good idea to look at a study in this field. Two scholars, John Aycock and Tara Copplestone (2018), was done an archaeological examination of an Atari 2600 game, the Entombed. In addition to shedding light on the term "Retrogame Archeology", there are two interesting findings in this study.

The Entombed Game

The Entombed, an Atari 2600 game released in 1982 by US Games. The player in this game is, appropriately, an archaeologist who must make their way through a zombie-infested maze. The maze in Entombed is particularly interesting: it is shaped in part by the extensive real-time constraints of the Atari 2600 platform, and also had to be generated efficiently and use next to no memory. The scholars reverse engineered key areas of the game’s code to uncover its unusual maze-generation algorithm, which they have also built a reconstruction of, and analyzed the mysterious table that drives it. In addition, they discovered what appears to be a 35-year-old bug in the code, as well as direct evidence of code-reuse practices amongst game developers.

They found that, variety of patterns shown in the maze generation relies on the pseudo-random number generator (PRNG) in the game code. PRNG was also include a bug and this bug is a very distinctive signature for it. They used this bug to identify programmers’ code reuse activity. Besides Entombed, they found this code in five other games. Three (M.A.D., Raft Rider, Towering Inferno) were also published by US Games; another, Q*bert, has people credited that intersect with the US Games games; the last one, Angriff der Luftflotten, appears to be a minor variant of M.A.D. It seems clear that the PRNG code either originated elsewhere and was copied into Entombed, or was copied from Entombed to other games.

You can watch the video below to get an idea about the game.

The second interesting point that scholars have found is related to the codes that make up the maze. Due to the constraints of the Atari 2600 platform mazes should be generated procedurally and should be reliably navigable in each time. Unfortunately reengineering of the game did not helped the scholars to understand the logic behind the maze generation procedure. The interview with one of the developers involved in the development of this game makes this situation more colorful.

Steve Sidley said:

‘The basic maze generating routine had been partially written by a stoner who had left. I contacted him to try and understand what the maze generating algorithm did. He told me it came upon him when he was drunk and whacked out of his brain, he coded it up in assembly overnight before he passed out, but now could not for the life of him remember how the algorithm worked.’

Sidley also observed that the maze code was uncommented, and when asked about the 32-byte table said
‘It was a mystery to me too, I couldn’t unscramble it. I just used it to generate the new row at the bottom of the screen.’ 

Maybe no-one ever really understood the logic of the algorithm. But there it is, in a 1982 Atari game, posing a seemingly unanswerable question. The fundamental logic that determines the next square is locked in a table of possible values written into the game’s code. Depending on the values of the five-square tile, the table tells the game to deposit either wall, no wall or a random choice between the two. It seems straightforward, but the thing is, no-one can work out how the table was made. Whatever the programmer did, it was a stroke of mild genius. Every time the game is played, a reliably navigable maze is pumped out. Were the table’s values random or even slightly different, the maze would likely fail to be drawn with a playable path through it. It just seems impossible to explain.

The act and experience of programming is, at its heart, a fundamentally human activity that results in the production of artifacts. The video games have become a major commercial enterprise and an important part of our culture. They store up their own record of human history. They are not just a technical product; they are a form of material culture which can be examined through archaeological lenses. It will not be wrong to say that in the distant future archaeologists will intensively do research on today's computer games to understand our lifestyle and culture.

Aycock, J., & Copplestone, T. (2018). Entombed: An archaeological examination of an Atari 2600 game. arXiv preprint arXiv:1811.02035.