surround (thing)

A game for the Atari 2600 in which two players control blocks that constantly move around on a grid, leaving deadly trails behind them. The goal is to make your opponent run into a trail first, typically by walling them into a small space. It was one of the more enjoyable two-player games for the system. The Surround cartridge also included a freeform draw mode, called "Video Graffiti," in which the player could use the same user interface to just doodle on the screen.

These days, people seem to generally refer to Surround's play mechanic as Tron, due to Tron's lightcycle scene. But Surround is the original that the lightcycles were based on. (Tron was released in 1982.)