Galaga is a fixed shooter arcade game developed and published by Namco in Japan and published by Midway in North America in 1981. It is the sequel to Galaxian, released in 1979. The gameplay of Galaga puts the player in control of a space ship which is situated on the bottom of the screen. At the beginning of each stage, the area is empty, but over time, enemy aliens fly in formation, and once all of the enemies arrive on screen, they will come down at the player's ship in formations of one or more and may either shoot it or collide with it. During the entire stage, the player may fire upon the enemies, and once all enemies are vanquished, the player moves onto the next stage. Galaga has proven very successful. The arcade version of it has been ported to many consoles, and it has had several sequels, most recently Galaga Legions for the PlayStation Network and Xbox Live Arcade services. The objective of Galaga is to score as many points as possible by destroying insect-like enemies. The player controls a starfighter that can move left and right along the bottom of the playfield. Enemies swarm in groups in a formation near the top of the screen, and then begin flying down toward the player, firing bombs at the fighter. The game ends when the player's last fighter is lost, either by colliding with an enemy or one of its bullets, or by being captured. Galaga introduces a number of new features over its predecessor, Galaxian. Among these is the ability to fire more than one bullet at a time, a count of the player's "hit/miss ratio" at the end of the game, and a bonus "Challenging Stage" that occurs every few levels, in which a series of enemies fly onto and out of the screen in set patterns without firing at the player's ship or trying to crash into it.