Galaga is a fixed shooter. The player mans a lone starfighter at the bottom of the screen, which must prevent the Galaga forces from destroying all of mankind. The objective of each stage is to defeat all of the Galaga aliens, which will fly into formation from the top and sides of the screen. Similar to Galaxian, aliens will dive towards the player while shooting down projectiles; colliding with either projectiles or aliens will result in a life being lost. Some enemies can morph into new enemy types with different attack patterns, with one even taking the form of the Galaxian Flagship. Stages are indicated by emblems located at the bottom-right of the screen. Enemies become more aggressive as the game progresses, increasing their number of projectiles and diving down at a faster rate. The third stage and every fourth thereafter is a bonus stage, where the aliens fly in a preset formation without firing at the player. Galaga was met with acclaim, with many applauding the addictive nature, gameplay structure, innovation and improvements over its predecessor, and was a popular game during the golden age of arcade video games. In Japan, it was the sixth highest-grossing arcade game of 1981, then the third highest-grossing arcade game of 1982, and then the ninth highest-grossing table arcade cabinet of 1986.