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Video Game Bugs That Turned Features

When Glitches Enhance Gameplay

Atahan Karaman
15 min readJun 1, 2024

This article was written by Ata Uzay Kuzey for the “Bilkent University, COMD 354 — Game Design and Research” course.

Computer games are prone to bugs in their programming. While most bugs get removed, some are too helpful or loved to be removed from the game, and thus, they become features. This article examines influential bugs from games such as Space Invaders, Street Fighter II, Super Mario Bros., Minecraft, and Civilization. It will analyze their history, causes, reasons for being kept in their respective games, and how they changed the design of their games and gaming culture.

Photo by rivage on Unsplash

The term “bug” has been used to describe a problem in a machine since the 19th century. It is not unreasonable to expect that a bug that occurs in a video game is a problem and needs to be fixed, which is generally the correct course of action. However, now and then, there comes a bug that is useful, loved, or funny, and the game developers decide to keep it in the game. This occurrence is coined by the community as “Bugs That Became Features,” and there have been a handful of examples throughout the years.

This paper will investigate the cases of bugs that became features through the years, using the examples of Space Invaders, Street Fighter II, Super Mario Bros., Minecraft, and Civilization. This paper will discuss the influential bugs from these games, why they occurred in the first place, why they were decided to be kept in the game, and how they changed their games and game culture.

Space Invaders

Space Invaders is a classic arcade game created by Tomohiro Nishikado and released by Taito in 1978. In this game, the player controls a laser cannon and defends against waves of descending aliens by shooting them before they reach the bottom of the screen. The goal is to destroy all the aliens and earn as many points as possible while avoiding being hit by enemy fire. The game is considered one of the most influential and iconic video games ever, helping to establish the shoot ’em up genre.

http://flyers.arcade-museum.com/flyers_video/taito/28031001.jpg
Space Invaders

Alien Speed Increase
Space Invaders is one of the most influential games ever, where players shoot aliens slowly approaching them. In the game, 55 aliens composed of 5 rows and 11 columns move in the directions of left, right, and downward, gradually getting closer to the player. The player should eliminate all the aliens while also dodging the projectiles shot by the aliens. As more and more aliens get destroyed, the remaining aliens start to move faster, making the game more challenging as it progresses. This behavior was not intended by the creator of the game, Tomohiro Nishikado, and it is one of the most famous bugs that turned into features.

The traditional games in Japan during the period were not built using microprocessors and computers, instead using analog electronic components. At the time, microprocessing was becoming more popular, especially after the release of the first game with a microprocessor, Gun Fight. This was mainly happening in the USA, and there was still little information in Japan about microprocessors, and there was no development hardware for creating games using microprocessors. So, to be able to create Space Invaders, Nishikado developed his hardware by referring to American boards. In the end, he completed the hardware and created Space Invaders.

The board's technical limitations were why aliens increased speed as more of them were destroyed. Nishikado originally wanted the 55 aliens to all move at constant speed simultaneously. However, the hardware Space Invaders was run on only allowed Nishikado to move one alien every 1/60th of a second. At the start of the game, it takes about a second for all the aliens to take a step, and this time frame decreases as the number of the aliens shrinks, making them move faster. When Nishikado discovered this bug, he thought it made the game more interactive and exciting, and it enhanced the game progression by introducing an escalating challenge, so he ultimately decided to make the bug into a feature.
With the low framerate of the hardware used then, the speeding up of the aliens didn’t require any additional programming. When one wants to recreate Space Invaders, this feature has to be recreated by specifically programming the behavior.

Street Fighter II

Street Fighter II is a classic fighting game developed by Capcom and released in 1991. Players select from a roster of characters, each with unique fighting styles and special moves, and compete in one-on-one combat. The objective is to deplete the opponent’s health bar using a combination of punches, kicks, and special attacks. The game is renowned for its competitive gameplay, diverse character lineup, and significant impact on the fighting game genre.

Capcom Arcade Stadium: STREET FIGHTER II -The World Warrior-

Combos
One of the most enjoyable and essential aspects of a fighting game is the combo system, where one can stack up moves to continue their attack, also called a combo. This feature was originally unintended and was discovered during a testing session in the level of Street Fighter II where the player is tasked with destroying a car. The developers realized it was possible to attack multiple times while the punch animation was still happening. The developers managed to place up to eight hits using near-perfect timing, but they didn’t think it would affect the gameplay significantly, so they just decided to keep the bug.

One of the reasons why the combo system became popular amongst Street Fighter II players is that linked attacks couldn’t be blocked easily like regular attacks in the game. This meant that contrary to what developers thought, the combo system gave players who knew it an advantage in the game. It also surprised players who didn’t know about the combo system. The next game, Street Fighter III, was implemented as a real feature with extra features like a combo bar. Combos have since become indispensable to the fighting game genre.

The original cause of the bug was the developers tweaking the input controls. The original intention of the change was to make super moves more accessible and possible. The resulting gameplay allowed the existence of time frames necessary to perform combos.

Super Mario Bros.

Super Mario Bros. is a platform game developed by Nintendo and released in 1985. Players control Mario (and optionally his brother Luigi in multiplayer mode) as he travels through the Mushroom Kingdom to rescue Princess Peach from the villain Bowser. The game involves running, jumping, and defeating enemies across various levels while collecting power-ups like mushrooms and fire flowers. It is celebrated for its innovative gameplay, iconic characters, and significant influence on the platforming genre and the video game industry.

Super Mario Bros.

Wall Jump
Starting from Super Mario 64, wall jumping has become a standard feature in many 3D Mario games. Even though the official introduction of the feature happened with Super Mario 64, the feature existed since the first installment of the Super Mario series, Super Mario Bros., as a bug that allowed players to wall jump with frame-perfect accuracy.

How this bug came to be is related to two features of the game. Firstly, for Mario to be able to jump, a ground check was performed. This was done using the 16 by 16 size of the tiles, so if Mario had a tile beneath him and aligned with the 16 by 16 grid, the ground check would return true. The second feature is that the tiles in Super Mario Bros. always push players outwards to stop them from getting stuck in the ground. The bug occurred when a player with enough velocity ran into a wall and got stuck in the wall for a single frame. If the jump button is pressed in that single frame, the game will identify the ground check as true and perform the wall jump.

The wall jump glitch still exists in the following series of installments, for example, in Super Mario Bros. 3. After the bug was proven too challenging to fix, it was implemented correctly in the 3D Mario games and became a feature of the Mario franchise.

Minecraft

Minecraft is a sandbox game developed by Mojang Studios and released in 2011. Players explore a blocky, procedurally generated 3D world, gathering resources, crafting items, and building structures. The game offers different modes, including Survival, where players must manage health and hunger while fending off monsters, and Creative, where they have unlimited resources and can freely build. Minecraft is acclaimed for its open-ended gameplay, creativity, and extensive modding community.

Minecraft

The Creeper
One of the most famous mobs from Minecraft is indubitably the creeper. It is a fictional mob, and its origin lies in a bug. In 2009, the creator of Minecraft, Markus “Notch” Persson, was trying to model the first passive mob in Minecraft, the pig, and he accidentally created the creeper as a bug. After seeing the model he created, he kept it in, as it looked interesting.

Earlier in the development of Minecraft, instead of using a modeling program to create the models, Notch was using code to create all the models for the entities and blocks in the game. During this process, he mixed up the values for the height and width of the pig entity, making it something tall instead of something wide. To demonstrate how a mistake like this can happen when creating graphics using only code, trying to create the same bug using the same programming language Minecraft is programmed in, Java, and the javax.swing library provided by Oracle. To simplify the situation, one can use a 2D model from the side to see the changes. The primary method will call a function to draw a pig using integer values for its coordinates and body proportions. Then, it will swap the height and width values and call the function again. Because of the difference in height and width properties, the other parts of the model will be distorted, too, creating a model that looks like a monster that later becomes the iconic creeper.

After Notch decided to keep the bug in the game to be a unique new creature, the new creature slowly turned into one of the most iconic fictional creatures in the gaming industry, shaping the marketing of Mojang Studios.

The program displays a pig's side profile and a distorted pig's side profile.

Quasi Connectivity
Redstone is one of the most essential components of Minecraft as it allows the construction of interactive and automated mechanical builds using an imaginary wire-like substance called Redstone. For the building process of circuits to be efficient and easy, the behavior of individual components should be understandable and intuitive. Contrary to this, Quasi Connectivity is an unintuitive behavior performed by three redstone components: Pistons, dispensers, and droppers.

Redstone components usually require to be directly powered up to work, which means that a redstone signal should be adjacent to the component, but the components listed above can work when the block directly above it is powered too, regardless of what that block is. This behavior is called Quasi Connectivity, and it can result in unintuitive situations where a piston can be powered by a Redstone block directly above it. However, this is not the end of the unintuitive behavior. The block must first be updated for a component to realize that it is powered up. Components emitting or transferring Redstone always send a block update signal to the blocks in its direct environment, causing any component to be updated and active. Quasi Connectivity can create situations where the redstone signal that activates the component is two blocks away, which causes them not to realize that they were activated. Any block update, which can be as simple as breaking or placing blocks near the Redstone components, causes the component to activate or deactivate. The Redstone community has used this feature extensively, and it is typically used to create a block update detector. With its weird behavior, Quasi Connectivity is originally a bug, and from the perspective of a new Redstone builder, it still looks like a bug, and bug reports are still being filed while the discussion about whether it should be removed continues. The response to any bug filings about Quasi Connectivity is listed as “works as intended.”

The reason for the existence of Quasi Connectivity is not easy to explain. Notch has been talking about programming a pulley block that pulls and pushes blocks since 2009. The first implementation came as a mod programmed by a user with the nickname Hippoplatimus. After seeing the piston mod, a developer from Mojang Studios, Jens “Jeb” Bergensten, got the code from him and incorporated it into Minecraft as a real feature, and Hippoplatimus still exists in the credits of Minecraft. It is rumored that while doing this, they copied the code from another Redstone component, the door. Because of the 2-block height of the door block, it can be activated when either the top block or the bottom block is powered up. The resulting pattern of blocks that can power a door is the same as the pattern of blocks that can power a piston. Even though it is not decisive proof, it strongly points to that origin.

Civilization

Civilization is a turn-based strategy game developed by Sid Meier and released by MicroProse in 1991. Players build and expand an empire from the ground up, starting from ancient times and advancing through history. The game involves exploring the world, founding cities, managing resources, researching technologies, engaging in diplomacy, and waging wars. The objective is to become the dominant civilization through various means, such as military conquest, cultural influence, or technological advancement. Civilization I is praised for its deep strategic gameplay and has spawned numerous sequels, becoming a landmark in the strategy game genre.

Nuclear Gandhi
Civilization is a game about leading a nation from mankind’s history into prosperity. There are numerous options to choose from, with one of them being India. In the game, the ruler of India is Mahatma Gandhi, a leader famously known for his peaceful protests against the British Empire. So, when AI Gandhi started nuking countries, it was noticed and spread as a hilarious bug present in the game. However, the creators and programmers who worked on the game have stated that this behavior is not possible and is just a rumor. Still, due to its popularity, Nuclear Gandhi was coded as an easter egg in a future installment of the series, Civilization V, where Gandhi's “use nuke” and “build nuke” parameters were set to the maximum possible value. So, Nuclear Gandhi is an interesting case of a rumor of a fake bug that turned into a feature.

The reasoning behind the cause of the bug is as follows. While making Civilization, every leader was given an aggression score out of ten, determining the likeliness of various acts, including nuke-building and nuking other countries. The aggression score of Gandhi was originally set to one. However, once a country instituted democracy, its aggressiveness decreased by two points. Since Civilization used 8-bit unsigned integers, the original value of one was stored as 00000001 in binary, while minus two was stored as 11111110 using two’s complement form. The addition of these two numbers resulted in 11111111, which, when interpreted as an unsigned number, resulted in 255 points for aggression, which caused Gandhi to become highly aggressive and start nuking countries.

The reasoning behind the rumor is an interesting case of integer overflow, and it made the bug believable so much that the bug was shown as an example of integer overflow at Harvard University. The creator of the game disproved every step of the reasoning. In the original game, the aggressiveness scales of the leaders could only be from one to three, democracy did not affect aggressiveness, and the language Civilization was programmed in C, assumed all integers to be signed, and since Sid Meier didn’t tweak that, an overflow wasn’t possible. Overall, it is safe to say that Nuclear Gandhi didn’t exist as a bug, and it was only a rumor. Even though it wasn’t a real bug, the Nuclear Gandhi lives on through memes and easter eggs, making it a real feature of the Civilization series.

Conclusion

In conclusion, the bugs present in the games Space Invaders, Street Fighter II, Super Mario Bros., Minecraft, and Civilization have found ways to include bugs in their game designs. Even though the causes of the bugs varied drastically, it was ultimately decided that they all served the game experience and were worthy of becoming a feature.
The bugs found in Space Invaders, Street Fighter II, and Super Mario Bros. changed the game industry and their respective genres by introducing new mechanics. The bugs found in Minecraft have either become one of the most iconic monsters of game culture or provided an incredible mechanical tool for players. The rumor of a bug in Civilization became an easter egg in the following series of installments. All the bugs are an indication of how accidental mechanics in games can provide an increase in the quality of the games.

References

Video Games Industry
Games
Game Design
Video Game Journalism
Video Game Development

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Atahan Karaman
Atahan Karaman

Written by Atahan Karaman

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Product Manager @ Lucid11 Interactive | Co-Founder, Instructor

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