Gorf

Gorf is an arcade game released in 1981 by Midway Mfg., whose name was advertised as an acronym for 'Galactic Orbiting Robot Force'. It is a multiple-mission fixed shooter with five distinct modes of play, essentially making it five games in one. It is well known for its use of synthesized speech, a new feature at the time.

The player controls a spaceship that can move left, right, up and down around the lower third of the screen. The ship can fire a single shot (called a 'quark laser' in this game), which travels vertically up the screen. Unlike similar games, where the player cannot fire again until his existing shot has disappeared, the player can choose to fire another shot at any time; if the previous shot is still on screen, it disappears.

Gorf consists of five distinct 'missions', each with its own patterns of enemies. The central goal of each mission is to destroy all enemies in that wave, which takes the player to the next mission. Successfully completing all five missions will increase the player's rank and loop back to the first mission, where play continues on a higher difficulty level. The game continues until the player loses all their lives. The player can advance through the ranks of Space Cadet, Space Captain, Space Colonel, Space General, Space Warrior, and Space Avenger, with a higher difficulty level at each rank. Along the way, a robotic voice heckles and threatens the player, often calling the player by his current rank (for example, 'Some galactic defender you are, Space Cadet!'). Some versions also display the player's current rank via a series of lit panels in the cabinet.

The missions are:

Astro Battles: The first mission is almost an exact clone of Space Invaders. This is the only mission that is not set in space, but rather against a sky-blue background. A small force of enemies (24 in Gorf vs. 55 in Space Invaders) attacks in the classic pattern set by the original game. The player is protected by a glittering parabolic force field that is gradually worn away by enemy fire. The force field switches off temporarily while the player's shots pass through it.
Laser Attack: In this mission, the player must battle two formations of five enemies each. Each formation contains three yellow enemies that attempt to dive-bomb the player, a white gun that fires a single laser beam, and a red miniature version of the Gorf robot.
Galaxians: This mission is a clone of Galaxian, with the key differences being the number of enemies (24 in Gorf vs. 46 in Galaxian) and the way the enemies fire (pellets in Gorf, missiles in Galaxian). Gameplay is otherwise similar to the original game.
Space Warp: Mission 4 places the player in a sort of wormhole, where enemies fly outward from the center of the screen and attempt to either shoot down or collide with the player's ship. It is possible to shoot enemy shots in this level.
Flag Ship: The Flag Ship is protected by its own force field (similar to the one protecting the player in Mission 1), and it flies back and forth and fires at the player. To defeat it, the player must break through the force field and destroy the ship's core: if a different part of the ship is hit the player receives bonus points and the part breaks off and flies in a random direction, potentially posing a risk to the player's ship. If the player successful hits the Flag Ship's core, the Flag Ship explodes in a dramatic display, the player advances to the next rank, and play continues on Mission 1, with the difficulty increased.