(10) GAME ANALYSIS - TETRIS

Contents:
Game Analysis: Tetris
Game Analysis: Centipede
Game Review: Pac Man

GAME ANALYSIS: TETRIS

DESIGNED BY ALEXEY PAJITNOV, RELEASED IN 1987

Few games are as universally well respected by game developers as Tetris. Often when a game becomes as popular as Tetris has, with versions for every system imaginable and untold millions in sales, gaming professionals start complaining about what a poor game it is. Myst is a good example of this. On its release, the title received near universal praise from the gaming press for being a fun adventure game in a beautifully conceived world. Game developers themselves, though not quite as enthusiastic, still thought it was a good game. Multiple millions of copies later with years spent on the best-seller charts, the same gaming press found reason to start hating the game and its amazing continued popularity. Game developers are particularly loud in voicing their dislike for the game. Is the game worse now? No, of course not. Do gaming professionals, press and developers alike, resent the game for its sales? It would appear so. But this is not the case with Tetris. Tetris conquered the world in terms of popularity, yet one is hard pressed to find anyone with a negative comment about the game. What is it about Tetris that makes the game immune to criticism? It would appear something about the game’s simplicity and clearness of design vision makes even the most cynical game developer concede the game’s greatness. Contrary to what happened with Myst, when Tetris was first released, most of the gaming press dwelled on the game’s origins in Russia and seemed underwhelmed, or at least unexcited, by the title’s gameplay. The game was so simple, its technology so lacking in razzle-dazzle that, perhaps, the press found themselves incapable of writing enthusiastically about the game—at least at first. Now that the game is an undisputed classic, any game critic will be happy to tell you about the hundreds of hours she spent blissfully lost in the game.

Gameplay in Tetris is exceedingly uncomplicated. The game-world is a tall, rectangular, 2D box. Blocks appear at the top of the box. The blocks are made up of four squares arranged in every possible pattern where all the squares share at least one side with another square. The blocks then slowly fall to the bottom of the box, and the player is able to move these blocks to the left and right, or rotate the piece in 90 degree increments. Once the player hits an obstruction, either the bottom of the box or another piece, the block stops moving, the player loses control of the block, and another piece appears at the top of the screen which the player can now control. When the blocks at the bottom of the screen form a horizontal line across the rectangle, that line of squares disappears, and any squares above that line move down one row. The player’s game is over once incomplete rows of the blocks fill up the rectangle and subsequent pieces are prevented from entering the play-field.

PUZZLE GAME OR ACTION GAME?

Tetris is often referred to as a puzzle game, and for good reason. Tetris has elements obviously reminiscent of a puzzle, with the player needing to find how blocks best fit together. In this way the game is similar to a right-angle jigsaw puzzle, or any number of other “organize these geometrical shapes in this small space” puzzles. An even better comparison would be the traditional game pentomino, from which Alexey Pajitnov, Tetris’s designer, is supposed to have drawn inspiration. In pentomino, one must take twelve different shaped pieces, each made out of five squares, and fit them into a square box. One can see the similarities, but at the same time Tetris changes the game into something entirely different, something entirely more challenging and compelling. Pajitnov could have just as easily made a direct adaptation of pentomino to the computer, as many other developers have done for jigsaw puzzles or “sliding number”-type puzzles. This might have been an entertaining program, though perhaps not as fun as the actual game itself since part of the fun of pentomino is the tactile nature of manipulating the blocks. But by taking the puzzle and changing it into a game that could only happen on the computer,
Pajitnov ended up creating a unique new game, which is far more entertaining than the original.

Many times when members of the computer game intelligentsia refer to a game as being a puzzle game, they do so with derision. For them a puzzle game is one that presents a series of static puzzles to the player, puzzles which never change and never react to the player’s actions. They argue that a game must provide a reaction to the player’s actions, and an opponent for the player to compete against. Hence, the critics would say, these so-called “puzzle games” are not really games at all, but just puzzles. Furthermore, often the puzzles found in these games have only one solution, further limiting the player’s interactive experience. Examples would include most all adventure games, such as Zork, Myst, or even Grim Fandango, games that, though they provide the player with a world to explore and challenging puzzles to complete, do nothing to create a unique experience for the player.
Tetris carefully balances action and puzzle elements to create a unique gameplay experience. Pictured here, and throughout this chapter: classic mode in The Next Tetris.

But Tetris is never criticized for this problem, because it so brilliantly combines the mechanics of a puzzle game with the mechanics of an action game in order to create a truly compelling gameplay experience. Thus everyone who plays Tetris, each time they play it, has a unique experience. One action game mechanic Tetris uses is the sense of an ever-approaching threat that the player has to address in a limited amount of time. In Centipede this threat is the anthropod winding its way down from the top of the screen. In Tetris it is the block dropping from above. If the player does not move and rotate the piece before it reaches the bottom of the screen, and if the player does not determine an optimal placement for this piece, the piece may get stuck in a location that blocks off lower rows from being completed, and the player gets one or more lines closer to ending his game. As gameplay progresses, the speed at which these blocks fall from the top of the screen increases, thus increasing the challenge for the player and ramping up the difficulty over the course of the game.

Another similarity between Tetris and action games that further distinguishes it from other puzzle games is the variety of gameplay situations Tetris can create: each game a player plays is unique. The play mechanics set up an infinitely large number of unique games, with each move the player decides to make influencing the rest of her game. The way a piece is positioned into the blocks already at the bottom of the screen directly impacts where the next piece can be placed. Should the player fill up the four-block-long slot with only two blocks from an upsidedown “L”-shaped piece? Or should she hold out, waiting for that desperately needed “I”-shaped piece? The “L” will not fill the slot completely, but no one knows how long it will be until the “I” piece arrives. In other cases the player may have a number of different positions in which to put a piece, and the player must think ahead, figuring out if she puts a piece in a given slot what sort of slots that will leave available for later pieces. The player constantly has to consider where future blocks will or will not be able to fit. A player may learn to recognize certain piece configurations, but every game is sufficiently unique that no player can be completely prepared for the challenges she may face.

TETRIS AS A CLASSIC ARCADE GAME

Indeed, there are many indications that Tetris is an example of what I call the “classic arcade game” form. This is despite the fact that it was not originally conceived for gameplay in the arcades (though its rampant popularity eventually led to its arrival there), and that it was created years after the classic arcade game form had stopped being used by professional arcade game developers. Looking over the list of classic arcade game qualities such as Single Screen Play, Infinite Play, Multiple Lives, Scoring/High Scores, Easy-to-Learn, Simple Gameplay, No Story etc. we can see just how Tetris fits the guiding principles of the form.
Single Screen Play: Of course, Tetris takes place on only one screen. The player is able to view the entire game-world at one time and make informed decisions about what he wants to do with a given piece based on that. There is no exploration component to the game, no way to really surprise the player (beyond what piece appears next), so the layer has all the information he needs to be successful at the game, and has nothing to blame but himself for failure.
Infinite Play: Tetris allows the player to keep playing until, through her own bad decisions, the blocks reach the top of the box. Every game ends in defeat, and no one can truly say she has “beaten” the game. Players can always find ways to improve their Tetris playing ability. This is a crucial difference between Tetris and a traditional puzzle. Once a player has solved a puzzle, if she remembers how she did it the first time, the puzzle will no longer present any challenge to her. People usually do not enjoy doing puzzles multiple times, whereas a well-designed game can be replayed forever. Tetris is just such a game.
Multiple Lives: Unlike most classic arcade games, the original Tetris implementation only offers the player one life. Once the blocks reach the top of the box, the player’s game is over. The design of the game, however, allows the player to see that he is doing poorly while not defeating him instantly. As the blocks stack up at the bottom of the rectangle, the player sees the mistakes he is making and has time to figure out how to better line up the blocks before his game is over. So, while Tetris does not offer the player multiple lives, it does give him a chance to learn the game well enough to achieve some minor successes before forcing him to start over.Despite being developed years after classic arcade games had fallen out of style, Tetris’s gameplay embodies many of the design principles of that genre of games.
Scoring/High Scores: Tetris uses a model for giving the player a score and recording it in a high-score table which is directly taken from the system used in games like Asteroids or Galaga. Indeed, since the game cannot be defeated, it is the possibility of achieving a higher score that can become the player’s true impetus to play the game again.
Easy-to-Learn, Simple Gameplay: Tetris truly excels in how simple and obvious its game mechanics are. The player really only needs three buttons in order to play the game successfully, and these all translate into obvious results on the screen. This means that virtually anyone, regardless of how familiar they are with computer games, can walk up to the game and start playing it immediately. However, a player will never be able to fully master the game due to the game’s ramping-up difficulty and the potential for infinitely long games.
No Story: Tetris has even less story than most classic arcade games, and is the case most often cited by people who want to point out that games do not need stories to be compelling for the player. The only sort of setting Tetris has is its origins in Russia, which has been used for various aesthetic effects in the different incarnations of the game. The first PC version of the game, as published by Spectrum Holobyte, included backdrops behind the gameplay that involved different scenes from Russian life, and the music sounded vaguely Slavic in origin. But once people learned what a great game Tetris was, subsequent implementations of the game, such as the one for the Nintendo Gameboy, had no Russian theme to them and had no setting or story at all. The game did not suffer one bit for this lack of story. Indeed, Tetris’s total lack of setting may actually be something that separates it from the classic arcade games, which all made an attempt to be grounded in a fantasy world of some sort, whether it was outer space in Galaga, insects in a garden in Centipede, or funky ghosts chasing a little yellow man around in Pac-Man. Tetris has no such pretensions, and thus stands out.

THE TECHNOLOGY

Another similarity between Tetris and classic arcade games is that none of those games relied on their technology to impress the player. For CAGs, the graphics the arcade machines in the early ’80s could produce were so lackluster compared to what players would find in other media, such as movies or television, that players had to be drawn in by something else. As a result, the gameplay had to be truly captivating for these games to survive. Despite the fact that much more sophisticated graphics were available by the time Tetris was released in the West in the late ’80s, the game did not need fancier graphics and stuck to a very simple 2D implementation. Tetris’s gameplay is so strong that it does not matter how technologically simple its implementation may be, the game is still wildly entertaining.

The implementation of Tetris is so simple that many aspiring game programmers start out by making a Tetris clone. Indeed, numerous companies have attempted to add fancy graphical effects to the game, including making it 3D. The first of these was probably Welltris, a sequel of sorts to Tetris, designed by Pajitnov. In Welltris, a 3D “well” takes the place of the Tetris box. Tetris-style pieces (though not always of four blocks) fall down along the sides of the well and must be lined up into rows on the bottom. The gameplay was considerably more complex without being particularly more fun or challenging. As a result, players were uninterested, and went back to the simplicity of the original. Many subsequent Tetris knockoffs attempted to make “improvements” on the original, either through fancy effects or special pieces of various sorts. None of these attempts were particularly successful, and players continued to want to return to the original.

The attempts to add technological sophistication to Tetris failed, not just commercially but also artistically. The enhanced technology added to these knockoff products was actually detrimental to the original game design, polluting its purity and making the game lose its elegance and fun in the process. Of course, the moral to the story is that enhanced technology is not necessarily beneficial to a given game, and game designers must be wary when the whiz-bang engine effects start to get in the way of what makes the game entertaining in the first place.

While Tetris may have not needed much in the way of computer technology to function, it is worth pointing out that there could be no Tetris without a computer. Tetris is not a game adapted from a pen and paper or board game, but rather something that only can exist in a world carefully controlled and governed by a computer. As mentioned previously, Pajitnov is said to have drawn his inspiration from the non-computer puzzle game pentomino. In adapting it to the computer,
Pajitnov changed it into a form which could exist only on a computer. The descending of the pieces from the top of the screen at a steady rate, the way they can interact with the pieces already at the bottom of the screen, and the random way in which pieces become available to the player are all operations only a computer program could provide while still allowing for an entertaining experience for the player. These are all tasks the computer performs expertly, and it was brilliant of Pajitnov to think to add them to his game.

ARTIFICIAL INTELLIGENCE

All the game has in terms of AI is the random number generator that picks the next piece to enter the play-field. However, the game mechanics are such that this random number is enough to completely change each game, presenting the player with unique challenges after every piece is dropped. Since the randomness ensures that the player never knows what the next piece will be, he is forced to play the piece in a way that is optimal for whatever one of the seven pieces comes along next. (Many incarnations of Tetris include a “next” feature, which shows the player the next piece that will come onto the play-field, a feature which does make the game a bit easier. Even when using this, however, players still do not know what the next-next-piece will be, hence they are still just making an educated guess as to where to stick the currently falling block.) If gameplay is about opposition, meaning an opponent providing a challenge to which the player must react, and if in solitaire computer games that opponent is the computer, then the fact that a random number generator provides all the challenge in Tetris demonstrates an important point. The AI the player faces only needs to be as smart as the game mechanics require. An AI needs to present the player with a situation that will challenge him, and it really does not matter how the AI arrives at that challenge. It could be as complicated as the AI for a deep strategy game like Civilization, or it could be as simple as the random piece picker found in Tetris. What matters is that the AI matches up with the game mechanics to sufficiently challenge the player.
Tetris has a very limited artificial intelligence that randomly picks the blocks which fall into the playfield. Despite its simplicity, this AI provides the perfect challenge for the player.

The random nature of which pieces arrive at the top of the screen might suggest to the reader that success at Tetris is just luck. If the pieces a player gets are random, how can different players’ scores be compared against one another? The key point to realize here is that, over time, the randomness of the pieces evens out. Just as die rolls in a board game even out over the course of the game, the random pieces passed to the player in Tetris end up functioning as if they were not random at all. Since there are only seven types of pieces, none with more than four blocks, and since the player (at least initially) has a large space in which to manipulate them, the randomness keeps the game from becoming predictable while still making one player’s game comparable to another’s. Over the course of a game, a player will get a few hundred pieces. The number of times the player gets just the piece she was looking for is evened out by the times she does not get the piece she wants. It may be that the player will fail to get exactly the right piece at the right time and that, since the player’s box is already full of pieces, the player’s game ends as a result. However, in order to get to a situation where she could not use whatever piece was given to her, the player had already made a number of mistakes to put herself in such a perilous situation. In the end, the random piece picker found in Tetris provides a fair, consistent challenge to all players.

ESCALATING TENSION

Tetris is very ruthless in the way it escalates tension throughout the player’s game. Unlike a game such as Centipede, the player gets no reprieve when a wave ends, nor does he get the ability to “start fresh” when he loses a life. In Tetris the player “dies” when the box fills up with pieces that fail to make complete rows, and his game is over, period. This means that the player must be constantly on his guard, constantly considering what to do with a piece before it reaches the bottom of the screen. Even a fast-paced game such as Doom provides the player with plenty of respites from the action. In that first-person shooter, there are safe corners to hide in and rooms where, once all the threats have been eliminated, the player can wait indefinitely without being threatened. Tetris never lets up and constantly confronts the player with a new challenge that must be addressed.

The only reprieve the player finds in Tetris is when she “battles her way back” from a tricky situation. Say the player has dropped some blocks in bad locations, thereby blocking off uncompleted rows below. Now the player’s game is harder because she has less space and time to manipulate her pieces before they are stopped at the bottom of the screen. The game’s tension has escalated as a result of the player’s mistakes. Now the player may be able, through careful placing of subsequent pieces, to erase the poorly placed bricks and finally complete the rows below. Now the game’s tension has decreased and the player is back to where she was, with more space and time to manipulate the falling pieces. The player feels a sense of accomplishment and relief. She is able to relax momentarily, knowing she has a “clean slate” to work with once again. Of course, this only lasts until the player makes another mistake, and then the game’s tension increases once again.

Further escalating the game’s tension is the acceleration of the speed at which the pieces fall over the course of the game. When the player’s score increases above certain specific amounts, the pieces in the game start moving at a faster rate, which makes the game more nerve-racking for the player. Since the pieces fall faster down the board, the player has less time to figure out the best position for a given piece, and also less time to manipulate the piece into that position. At the game’s fastest speed, most players will be incapable of placing a piece in an ideal location, and with a piece in the wrong place the game only gets harder. Just before the speed increases, the player might start to feel that he has mastered the game and could play Tetris indefinitely. But when the speed increases, whatever sort of rhythm the player had established is thrown off. Now the player needs to do everything he was doing before, only faster.

Once the player starts making mistakes in Tetris, these mistakes compound, making the game harder and harder to play. As the player fails to create rows at the bottom of the screen, the player has less and less space in which to manipulate his pieces. When the player accidentally drops a piece in the wrong location, that piece may block rows below from being completed, and will make it harder to maneuver subsequent pieces around that ill-placed piece. When the player tries to hold out for an “I”-shaped piece to fill a narrow column of empty spots, the player will have to keep placing other pieces in perhaps less-than-perfect locations until that piece randomly arrives. In all these ways, Tetris penalizes the player for failure. Instead of giving the player a chance to catch up as some computer games do, Tetris just punishes her, making it even harder to come back from errors made previously. Further complicating matters are the bonus points the player receives for removing four rows all at once with an “I” piece. With this tactic, the game tempts the player into taking potentially game-ending risks.

SIMPLICITY AND SYMMETRY

Tetris, as has been discussed, is a very simple game. A big part of its success is due to its simplicity and that it is so easy to learn while being so relentlessly challenging. The player does not need to learn any special moves in order to play the game. There are a very small number of keys used by the game, and those keys produce very obvious results on the screen. It is interesting to look at the pieces used in Tetris. They are all composed of four squares, and, in fact, the seven different types of pieces used in the game represent every possible combination of four squares, where each square must share a side with another square in its group. Since the player can rotate the pieces to whatever orientation he wants, there are only seven truly unique combinations of squares possible.
All of the pieces in Tetris are composed of four squares, each of which shares at least one side with another square. This gives the game an inherent consistency and balance.

It has been reported that Pajitnov, in creating Tetris, originally considered using pieces consisting of five squares combined into twelve unique pieces. Indeed, the pentomino game from which Pajitnov drew his inspiration used twelve five-square pieces. Pajitnov soon realized that this was too many different pieces to have to manipulate in Tetris’s high-pressure setting, where the player has a limited amount of time to find a perfect fit for a given piece. Certainly a game using five-square pieces could have been challenging in its own way, and perhaps a slower falling speed and larger play-field could have compensated for the added complexity of the larger pieces. But would it have been Tetris? No. Would it have been as fun and addictive as Tetris? Probably not. At some point a complexity level begins to stifle the core nature of a game, and confuses players instead of challenging them. Using five instead of four squares ruined the simplicity Pajitnov was striving for, and as a result he reduced the number of squares a piece could have.

There are actually thirteen unique combinations of five squares possible, where each square shares a side with another square. So it would appear that the original pentomino game, with its twelve blocks, did not use a complete set of pieces. I have never tried pentomino, so I have no idea how much fun that puzzle may be. Part of what makes Tetris so elegant is the completeness of its pieces. Every possible permutation of four squares with squares sharing sides is used in the game. Remove any one of the pieces from Tetris and the game’s balance would suffer. When playing, players will find themselves presented with situations that cry out for certain pieces. Certain arrangements of the blocks on the bottom of the screen leave holes that can only be perfectly filled by a specific Tetris piece. Part of what lends Tetris its balance is the fact that Pajitnov was wise enough to include each piece possible, thus providing a piece for every type of gap. The natural completeness and symmetry of the pieces available to the player in Tetris is a crucial component of its balance.

TEN YEARS ON, WHO WOULD PUBLISH TETRIS?

One must wonder, if Tetris were created today, what publisher would be willing to publish it. Originally Tetris was sold as “the game from Russia” and was attached to art and music of a similar nature, almost as a gesture to our new friends in what was then the U.S.S.R. Had Tetris been dreamed up by a kid in a garage in Iowa one wonders if it ever would have been published at all. (One would like to be optimistic and think that he would have been able to code it up, release it as shareware on the Internet, and the game’s fame would still have been assured.) Tetris is the ultimate in low-technology gameplay, and many game publishers simply refuse to publish games that do not utilize the latest in computer graphics wizardry. After all, where will they find the pretty screenshots for the back of the box? The game lacks any sort of story or even setting; another absolute must for the people in marketing. What sort of copy will they write in their ads? Indeed, it is a testament to Tetris’s brilliant gameplay that it cannot be adequately described in any amount of words, much less in a catchy one-liner. Even looking at a static screenshot of Tetris is a thoroughly unexciting experience, one which cannot hope to communicate the game’s sublime art. Gameplay is an elusive subject for manipulators of the written word; it must be experienced to be understood.

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