So, the candidates that remain are Pong: Computer Space; Baer's Brown Box; Spacewar!; Tennis for Two; and OXO. All of these are documented to exist, so there's no question of practical implementation for any of them - least of all Pong. In terms of video signal, Pong, Computer Space and the Brown Box generate a raster signal suitable for an NTSC television - whereas SpaceWar!, Tennis for Two, and OXO generate an X-Y signal for display on an oscilloscope or vector monitor. OXO's display is a little contentious - while it did use a cathode ray tube and it was driven by a signal, the display wasn't really intended to be a graphical one. In fact, the cathode ray tube wasn't chosen because of its display capability at all - in the early days, CRTs were used for storage. One implementation was called the Williams-Kilburn Tube, and it relied on a curious side effect of energised phosphors - once lit by the scanning electron beam, a charge would persist for a fraction of a second. This secondary emission could be sensed, then the phosphor re-charged on the next scan: meaning you could store an array of a couple of thousand bits indefinitely. This was presented on the face of the display as a grid of illuminated dots - the electron beam scanning rows in a fairly similar way to a raster display. However, a sensor sheet on the face of the tube did cover up most of the visible pattern, making this arrangement less than ideal for use as a display - but quite often a second tube would be connected in parallel without the obstruction. EDSAC, the machine that ran OXO, didn't use a Williams tube for storage - it used mercury delay line memory instead - but the contents of this memory were displayed on a diagnostic CRT in the same manner. So while it was never really intended to be used for graphics, the fact is it was - and so it still qualifies. Back to the candidates: in terms of interactivity I think most here count - again, the only possible exception is OXO. Because of the limitations of the display, OXO is considerably less dynamic than the other examples - with the display only updating when a move is made. That said, the display does change in response to player input. So it is interactive, if not exciting. Intent is the fourth criterion: and it's fairly clear that Pong, Computer Space and Baer's Brown Box were all intended for entertainment - that was their ultimate commercial purpose. Spacewar! was definitely a diversionary pursuit, and is frequently described as a game. Tennis for Two was an exhibit intended for public display - and it may have had an ulterior motive to kindle an interest in science - but the prime appeal was in the playing. Now, OXO. OXO was the product of study at Cambridge University - a practical proof as part of a thesis. If we take it as part of a PhD, the work is purely academic - but I think it's fairer to judge it on its own merits. As a piece of software, it stands alone as what could easily be described as a 'computer game', so while entertainment isn't the purpose of implementation - it was the purpose of playing. So the final test: can the game be played with no other visual output than the video display? Pong and Computer Space qualify without question. They are undoubtedly video games. Few would argue otherwise. You could say that the Brown Box's use of screen overlays for some of its games disqualifies it on this point - and there is some merit to this in cases where the plastic overlay is absolutely necessary to play. But for most of the games it's not - just an accessory - and the basic Tennis game doesn't have an overlay at all, so the Brown Box gets a pass. It's a video game. Spacewar! ran on the PDP-1, which was a modular system with a range of potential visual outputs. The CRT monitor was central to the game, but it wasn't the only output that SpaceWar used. In some versions, game scores were printed. However, these aspects are secondary to the actual gameplay - so Spacewar! is a video game. Tennis For Two is simpler: its only output was the oscilloscope display, so it is a bona fide video game. What about OXO? Like Spacewar! it ran on a full computer system, with its CRT display, line printer - and banks of valves and das blinkenlights. The question is: is it possible to play a full game with only the video display? The answer is... yes. With the caveat that you have to know what you're doing. If you memorise which number corresponds to each grid position (or at least make use of a printed reference) then it's entirely possible to play without any other output. It's clumsy and archaic - your moves are input on a rotary telephone-style dial - but poor controls are no reason to discount it. There are plenty of video games with terrible controls. So OXO is, without doubt, a computer game played on something which can be described as a video display. Under any reasonable definition, I think that qualifies as a video game. It might even be the first. However, to be sure it might be worth further investigation: a closer examination of the environment that spawned OXO may turn up some other potentials. What we think of as video games really comprise multiple strands: Arcade machines; Television games; Electronic games; And more recently, Virtual Reality; And Mobile Games, which have rapidly become a significant part of the video games industry. When we tease out these strands, the reason why it's so difficult to pin down the 'first' video game becomes apparent. Each of these strands has its own history: its own progression; and its own origin. If we look at them individually, the picture becomes much clearer: The first arcade video game? It's either Computer Space or Galaxy Game, both from the end of 1971. The first television game? Ralph Baer's Brown Box. The first electronic handheld video game? It could be the Game Boy, unless you count the Atari Lynx prototypes from 1987. The first virtual reality video game? Possibly played via the VPL Research EyePhone in 1987, or the Virtuality from 1991 - although research in head-mounted displays goes all the way back to the 1950s. And the first mobile game? Tetris, on the 1994 Hagenuk MT-2000. Nokia's Snake gets an honorable question. So when we split video gaming into its components, the question becomes much easier to answer - and the oldest strand becomes obvious. It's computing. The first video game was almost certainly an early computer game like OXO - it's just a question of determining the earliest example that qualifies. The good news is, computers weren't exactly common in the 1940s and 50s - and fewer still had video displays. In the brief window between the invention of the Williams tube circa 1946 and OXO in 1952, there are seven potential machines. Three of these potential computers were located at the University of Manchester, where the Williams tube was developed. The first was the Manchester Baby, operational in 1948 - a prototype, which was replaced by the full-scale Manchester Mark 1 in 1949. This in turn was developed into and replaced by a commercial model: the Ferranti Mark 1, operational in early 1951. There were two other British machines: The Pilot ACE at the National Physical Laboratory in Teddington, London - operational in mid-1950; And EDSAC at Cambridge University, which was first operational in 1949. At this time, the Americans had two machines with a video display: the Whirlwind I, built by MIT for the US Navy - partially operational in 1949, and reaching full capacity in 1951; And the Standards Western Automatic Computer, or SWAC - located in Los Angeles. It's impossible to know every program that ran on these early machines - but most of them are fairly well documented. Access was exclusive, and programs were filed in a job queue. There was normally a paper trail, and there was an incentive for institutions to highlight their machine's accomplishments. Unfortunately, this transparency and a need to justify the computer's existence meant that games were a very low priority.