Kill screen

A kill screen is a stage or level in a video game (often an arcade game) that stops the player's progress due to a programming error or design oversight. Rather than "ending" in a traditional sense, the game will crash, freeze, or behave so erratically that further play is impossible.

Video games, like any other computer software, can suffer from bugs. A bug in a video game is not automatically a kill screen; to be one, the bug must occur consistently in the same point in the game and must preclude any further play. While almost any type of bug could cause this sort of behavior, the most common cause is integer overflow of the level counter or simple oversight on the part of the game's programmers.

Kill screens were much more common during the Golden Age of Arcade Games. Games from this era were often written with the assumption that the player would stop playing long before the numerical limits of the game code were reached. Additionally, the limited hardware of these early machines often meant that programmers could not spend memory on logical checks of the state of the game.

Famous kill screens

While probably not the first game to suffer from a kill screen, "Pac-Man"'s is possibly the most famous. "Pac-Man"'s level counter was a single 8-bit byte, and could therefore store only 256 distinct values (0–255). Reaching the 256th board causes a counter that is used while drawing the fruit to overflow to zero, causing 256 fruit and seven blank spaces to be drawn. It can, however, be fixed with a patch. [cite web
title = Pac-Man's Split Screen level analyzed and fixed
author = Don Hodges
accessdate = 2008-05-09
url = http://www.donhodges.com/how_high_can_you_get2.htm ]

"Donkey Kong" also featured a kill screen in the 22nd stage, the 117th screen. This is an example of a kill screen that is not due to an integer overflow in a level counter (since programmers prevented this) [cite web
title = How High Can You Get? The fix for Donkey Kong's Kill Screen
author = Don Hodges
accessdate = 2008-05-09
url = http://donhodges.com/how_high_can_you_get.htm ] , but a different oversight on the part of the designers. The amount of time allowed for any given screen is determined algorithmically during play by the level the player is on. The timer is calculated 100*(10* (level + 4)), and has a maximum value of 8000. When the level reaches 22, the game reads 100*(10*(22+4)) or 100*260. However, the 8-bit counter rolls over at 256, meaning the game calculates 100*4. This causes the timer to be set so low that there is simply not enough time for the screen to possibly be completed. [cite web | title = Donkey Kong Kill Screen on Level 22
author = phantomdj
accessdate = 2008-05-09
url = http://www.youtube.com/watch?v=UmkhXdSC62w ]

"Dig Dug" also experiences a kill screen on the 256th round, which is counted as round zero, and the resulting integer overflow results in an enemy starting on top of the player's character, instantly killing him. [cite web
title = Dig Dug new World Record Kill Screen
author = AtHomeTech
accessdate = 2008-05-09
url = http://www.youtube.com/watch?v=600bQMqrEBE ]

"Duck Hunt" features a kill screen on level 100, causing the game to call it round zero, and lock up the game. If the level is defeated with a certain cheat code, the game starts over at round one. This is probably due to an overflow in a BCD math routine. [cite web
title = Duck Hunt level 100 error
author = raydempsey
accessdate = 2008-05-09
url = http://www.youtube.com/watch?v=AjUpe7Oh1j0 ]

While "Galaga" does not feature a true "kill screen," it does feature a few glitches upon reaching the 256th level, depending on the difficulty setting. [cite web
title = Galaga Stage 256 on Medium Skill
author = phantomdj
accessdate = 2008-05-09
url = http://www.youtube.com/watch?v=FZHqlfQnR9I ]

References

See also

*Glitch
*Screens of death