Centipede is a vertically oriented shoot ‘em up arcade game produced by Atari, Inc. in 1981. The game was designed by Ed Logg along with Dona Bailey, one of the few female game programmers in the industry at this time. It was also one of the first arcade coin-operated games to have a significant female player base, after Pac-Man. The player defends against centipedes, spiders, scorpions and fleas, completing a round after eliminating the centipede that winds down the playing field. The player is represented by a small, “somewhat humanoid head” at the bottom of the screen. The player moves the character about the bottom area of the screen with a trackball and fires laser shots at a centipede advancing from the top of the screen down through a field of mushrooms. Shooting any section of the centipede creates a mushroom; shooting one of the middle segments splits the centipede into two pieces at that point. Each piece then continues independently on its way down the board, with the first section of the rear piece becoming a new head. If the head is destroyed, the section behind it becomes the next head. The centipede starts at the top of the screen, traveling either left or right. When it hits a mushroom or the edge of the screen, it drops one level and switches direction. Thus, more mushrooms on the screen cause the centipede to descend more rapidly. The player can destroy mushrooms by shooting them, but each takes four hits to destroy. If the centipede reaches the bottom of the screen, it moves back and forth within the player area and one-segment “head” centipedes are periodically added. This continues until the player has eliminated both the original centipede and all heads. When all the centipede’s segments are destroyed, a new centipede forms at the top of the screen. Every time a centipede is eliminated, however, the next one is one segment shorter and is accompanied by one additional, fast-moving “head” centipede. A player loses a life when hit by a centipede or another enemy, such as a spider or a flea. The flea leaves mushrooms behind when fewer than five are in the player area, though the number required increases with level of difficulty. Spiders move across the player area in a zig-zag fashion and occasionally eat some of the mushrooms. Scorpions poison every mushroom they touch, but these never appear in the player’s movement region. A centipede touching a poisoned mushroom hurtles straight toward the player’s area. Upon reaching the player’s area, the centipede returns to normal behavior.

Similar to Centipede, the object of the game is to destroy a millipede that advances downward from the top of the screen. The millipede travels horizontally until it either hits an obstacle or reaches the edge of the screen, after which it drops one row and reverses direction. Once it enters the player’s gray maneuvering area, it stays there and extra heads appear at intervals until both they and the millipede are destroyed. Shooting a body segment splits the millipede in two, with the rear portion sprouting its own head. A collision with any enemy costs the player one life. New enemies and gameplay elements are introduced in Millipede: Earwig: same as the scorpion in Centipede, making mushrooms poisonous so that the millipede will charge straight to the bottom of the screen after touching them. Bee: same as the flea in Centipede, dropping mushrooms in a vertical line and requiring two shots to kill. Spider: same behavior as in Centipede, bouncing irregularly across the player area and eating mushrooms. Multiple spiders can appear at the same time on higher levels. Inchworm: when hit, slows all enemies for a short period of time. Beetle: crawls around the player area for a while, then climbs up and leaves the screen, turning any mushrooms it touches into indestructible flowers. When hit, everything on the screen scrolls down one row. Dragonfly: drops mushrooms while zigzagging down, and can be destroyed with a single shot. Mosquito: bounces off the sides of the screen as it descends diagonally. When hit, everything on the screen scrolls up one row. DDT bomb (stationary): can be blown up with one shot, destroying all enemies and mushrooms within the blast radius. Whenever the mushrooms scroll down, a new bomb is added at the top of the screen. Up to four bombs can be in play at one time. The player scores points for shooting the bomb itself, as well as increased values for any enemies destroyed in the blast. All flowers and poisoned/partially destroyed mushrooms revert to normal, whole mushrooms and score points during the process when the player loses a life. At regular intervals during the game, the player will face a swarm of enemies (bees, dragonflies, etc.) instead of the usual millipede. Each enemy destroyed awards increasing points, up to a maximum of 1,000 points per enemy; this attack ends when either the entire swarm has passed or the player loses a life. Also, at intervals new mushrooms will grow on the field while others die off, in a pattern similar to Conway’s Game of Life. Players can also choose at the start of the game whether to play at an advanced level, starting with a score that is a multiple of the number of points needed to earn an extra life (by default, 15,000). The gameplay is generally much more advanced than it would be had the player started with a score of 0 and worked their way up to that point level. The maximum advanced level allowed is a function of the preceding player’s score, and games started at an advanced level where the player did not earn at least one extra life are not eligible for the high scoreboard.