Light cycles are fictional vehicles designed by Syd Mead for the simulated world of the Tron universe. These futuristic two-wheeled vehicles resemble motorcycles and create walls of colored light. The vehicles were primarily used in a competition between humanoid computer programs, similar to an old computer game sometimes known as "Surround" or "Dominos" (games which predate Tron). Players are in constant motion on a playfield, creating a wall of light behind them as they move. If players hit a wall, they are out of the game; the last player in the game wins. Since the original display in Tron, there have been numerous adaptations, as well as references in popular culture.
A light cycle toy, in red and yellow versions, was produced by TOMY as part of the merchandising for the Tron film, along with action figures scaled to fit inside the toy cycles. Bootleg versions of TOMY's design were produced by other toy manufacturers that came in a wide variety of colors, including blue and silver, but were noticeably smaller than the TOMY-produced toy, too small in fact to accommodate one of the TOMY action figures.
In Kingdom Hearts II, Sora is forced to play the light cycle game with the Heartless to save Tron.
Light cycles make a return in Tron Legacy, with new designs by Daniel Simon. According to the press conference at Comic-Con 2009, a new vehicle appears called a "Light Runner," a two-seat version of the light cycle. It is said to be very fast, and has the unique ability to go off the grid on its own power. We also get a glimpse at Kevin Flynn's own cycle, a "Second Generation Light Cycle" designed in 1989 by Flynn and “rumor has it it's still the fastest thing on the grid.” It incorporates some of the look of both films.
The tie-in video game Tron: Evolution, which is set between the events of Tron and Tron: Legacy, features light cycles in sections of the single-player mode and in certain game maps for the multiplayer mode. Light cycle use in multiplayer gives players the option to shift back and forth between cycle and foot travel at will, and provides multiple attack and defensive options beyond the classic "boxing in" of an opponent. In addition, the light cycles of Evolution can pass through their own light trails (and the trails of allied players) unharmed.
A more classic interpretation of the lightcycle game is shown in the Wii-Game Tron Evolution: Batte Grids, which is primarily based on offline multiplayer or singleplayer matches. The lightcycle battles (one disceplene besides others like hyperball, grid tanks and lightrunners) don't allow the player to drive through his own trail, however if you play on a team, you can drive through the trails of your teammates, but still not through your own. These lightcycle battles take place only on the bikes, there is no possibility to change between the bike and running around on foot, which underlines the fact that this is a more classic version of the lightcycle game.