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Description

In the original Donkey Kong arcade game when you get to the 22nd stage (117th screen) there is a bug in the game's programming that causes the timer to have a time limit of 4 seconds, which is an insufficient amount of time to complete the level. As a result the timer runs out after the first few seconds causing Mario to die and eventually cause the player to lose all their lives. It should also be noted that the kill screen occurs near a point where the player can get over a million points.

Why it happens

Like most kill screens, this kill screen is the result of integer overflow on an 8 bit variable. 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 in seconds as 10×(level + 4), and has a maximum value of 80. When the level reaches 22, the game reads 10×(22+4) or 260 seconds. However, the 8-bit counter rolls over at 256, meaning the game calculates 4. This causes the timer to be set so low that there is 4 seconds for the player to complete the level, simply not enough time for the screen to possibly be completed, Unless you are playing on Japanese Set 3. On that version, there is a bug in 25m where if you jump at a certain point, you fall through the floor, Then Mario’s y position overflows to 0, and you complete the screen.

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