Portal, released by Valve in 2007, introduced the Sentry Turret as a small, tripod-mounted robot that guards test chambers with cheerful recorded lines and sudden gunfire. The firing sound became closely associated with the game's dark humour, where a polite machine could turn lethal in an instant. As Portal clips spread through gameplay videos and memes, the short burst became a shorthand for automated danger, and editors still use it today because it is instantly recognisable even without any image of the game itself.