system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Arcade "Kill screens"?
gpt
The simplest way to describe it is to say that a killscreen comes from being asked to perform a task that is impossible from a strictly literal perspective. 

Lets say you have a simple task--moving sand from pile A into pile B using only a spoon.  You have a time limit of five minutes to do this, and you are only able to move your arms at a fixed speed.  Each time you finish moving pile A to pile B, pile A is replaced with an even bigger pile of sand and you have to perform the task again.  If you keep repeating this pattern, eventually the pile of sand is too big to move in five minutes.

The most common example of this is Donkey Kong, where the killscreen represents a level where you are forced to get to the end in an amount of time that is strictly impossible to complete not only practically, but in theory.