Controlling a starship, the player is tasked with destroying the Galaga forces in each stage while avoiding enemies and projectiles.

Inspiration for the dual fighter mechanic was taken from a film that Yokoyama had seen prior to development, where a ship was captured using a large circular beam.

The player mans a lone starfighter at the bottom of the screen, which must prevent the Galaga forces from destroying all of mankind.

[6] Should additional lives remain, the player has an opportunity to shoot down the Boss Galaga holding the captured ship.

[6] However, destroying a Boss Galaga with a captured ship while it is in formation will instead cause the fighter to turn against the player and act as an alien.

[6] Enemies become more aggressive as the game progresses, increasing their number of projectiles and diving down at a faster rate.

[8] This new arcade board was named the Namco Galaga and was used in games including Bosconian (1981)[12] and Dig Dug (1982).

[8] The tractor beam emitted by the Boss Galaga was inspired by a film in which a character's ship was captured by a circling laser.

[8] While planning, lead programmer Tetsu Ogawa informed him of a bug whereby enemies would simply fly off the screen instead of moving into formation.

[8] Ogawa expressed interest in incorporating the idea into the game, leading to the inclusion of the Challenging Stages.

[8] Prior to location testing, the team focused on designing the instruction card, a sheet of paper that showed how the game was played.

[8] The card originally showed the control layout and the basics of the game, which was stripped early on for being too boring.

[8] Despite the game's immense popularity around the company, early location tests failed to meet expectations due to players being able to progress a long way with only one coin, thus generating low income.

[8] Although Yokoyama stated that the game's popularity could still generate income, Namco executives instructed the team to increase the difficulty level.

[18] In Europe, Aardvark Software released an unofficial port for the BBC Micro and Acorn Electron called Zalaga in 1983 which was described by Computer and Video Games as "true to the arcade original".

[59] Japanese publication Amusement Life said that the sense of thrill and fast-paced action made Galaga a "must play", while also praising its unique dual-fighter mechanic and colorful graphics.

[60] Vidiot magazine listed it as the seventh best arcade game of 1983, saying that its gameplay variety, dual-fighter mechanic and bonus stages made it stick out from the crowd.

[61] In a 1998 retrospective review, AllGame said the strategy stood out amongst other games of its type, describing the gameplay as "perfectly balanced shooting action.

[50] GameSpot, in their review for the Xbox 360 release, stated the gameplay was "as tricky as it ever was", praising the inclusion of online leaderboards and for being a faithful arcade conversion.

Nintendo Life praised the 3DS Virtual Console port of the NES version for remaining accurate to the original, stating that it "aged surprisingly well" and was worth revisiting.

[62] Joystick magazine praised the NES version's accurate portrayal of the arcade original, notably in its graphics and gameplay structure.

Eurogamer expressed distaste towards the Xbox 360 port's high price point, as well as the achievements for being "insultingly easy" to obtain.

[75] Shortly after the game's release, Namco produced miniature Galaga cabinets for buses and airplanes, housed in small 17-inch CRT monitors.

[81] Galaga has made cameo appearances in films including WarGames (1983),[82] The Karate Kid (1984),[82] Planes, Trains and Automobiles (1987),[82] The Avengers (2012),[82] and Pixels (2015).

[84] Hallmark Cards released a Galaga arcade cabinet ornament in 2009, which played sound effects from the game.

[86] Galaga is also the subject of several high score-based tournaments; as of 2020, the world record is held by Jordan Dorrington with a score of 20,980,450 points.