Kill screen

File:Split Screen in Pac Man.gif

The 256th and final level in Pac-Man, considered to be unplayable under normal circumstances

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 simple oversights on the part of the game's programmers such as an integer overflow of the level counter.

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; most games from this period were intended to continue until the players lost all of their lives. 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.

Notable kill screens

Pac-Man

Further information: Pac-Man § Split-screen

Pac-Man has a famous kill screen. The game's level counter was a single 8-bit byte, and could therefore store only 256 distinct values (0–255). Reaching the 256th level causes a counter that is used while drawing the fruit to overflow to zero, causing 256 fruits and seven blank spaces to be drawn. It can, however, be fixed with a patch.

Donkey Kong

Donkey Kong also featured a kill screen in the 22nd stage, and 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), 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. Steve Wiebe, a competitor from Redmond, Washington, got this screen when he attempted to beat Billy Mitchell's Donkey Kong high score on G4TV at E3 2009. It was the first kill screen to be broadcast on live television.

Mario Bros.

Mario Bros. has another famous kill screen. The game's level counter was a single 8-bit byte and therefore it could only store 257 levels, 1 more than the original Pac-Man. Reaching the 257th level causes a counter that is used while drawing the pipes to overflow to zero, causing 257 pipes and eight blank spaces to be drawn. However, it can be fixed with a patch.

See also

• Glitch
• Screens of death