Stargate

Stargate (also known as Defender II in re-releases) is an action game developed by Vid Kidz that was first released in arcades by Williams Electronics in 1981. The game was later ported to several home game consoles and computers including the Atari 2600, Apple II, and IBM PC. It is the sequel to Defender and has similar gameplay along with a few new features including new ships added to the enemy fleet and a cloaking capability for the player's Defender ship.

As in Defender, players control a spaceship above a city on horizontally scrolling screen which wraps around. A scanner at the top of the screen indicates where in the playfield the player is along with all of the humanoids and aliens. The city is along the bottom of the screen (represented by a mountainous looking line). The game starts with 10 humanoids in the city that players need to defend from the alien invaders. Numerous landers on each level will attempt to capture the humanoids and carry them to the top of the screen; if successful, the humanoid is transformed into an enemy mutant. Players need to prevent this by destroying the enemy landers before they capture humanoids, or if a humanoid is captured by rescuing it before it reaches the top of the screen. Humanoids can also be be shot by the player, so when flying low players need to be careful to not accidentally shoot any humanoids themselves. If all of the humanoids are lost, the city is destroyed; Similar to Defender, this doesn't end the game but rather increases the difficulty by having numerous, difficult to destroy mutants attacking. To complete a level and move on to the next, more difficult round, players need to destroy all of the aliens (with an exception for certain types).

The player's Defender ship has several weapons and defenses. The ship can fire a beam in the direction it is facing (players can fly both to the left and right) and it is equipped with a limited number of smart bombs that destroy everything on the screen. The ship can enter hyperspace to escape from dangerous situations (although player's need to be careful using hyperspace; the location the ship reappears is random and there is no guarantee it won't be right on top of an alien or some other danger). New to Stargate is an ability for player's to use the ships Inviso cloaking device; while using the Inviso cloak, the ship is invincible and can also touch any of the enemy invaders to destroy it. The amount of time the Inviso cloak can be used is limited; each use lasts for about 2 seconds, and the game begins with about 6 seconds available in total.

On each level there is a stargate which appears as a series of concentric rectangles. The stargate can perform one of several actions when players fly into it depending on what happens to be going on in the game at the time. Ordinarily, the stargate instantly transports the players ship to the opposite side of the playfield. If, however, one or more humanoids has been captured by a lander, the ship is transported to the captured humanoid nearest the top of the screen. If any humanoids are midair and falling, the ship is transported there so players can attempt to catch the falling humanoid. On the first 10 levels players can use the stargate to warp to a later level by carrying at least four humanoids and then entering the stargate.

Enemies invaders in Stargate are a mix of aliens previously found in Defender along with several new types. The aliens encountered are as follows:

• Lander: Landers appear on every wave of the game and attempt to capture humanoids.
• Mutant: Mutants are created when a lander successfully carries a human to the top of the screen. They attack players aggressively and are difficult to shoot due to their quick, erratic movements.
• Baiter: A fast ship that only appears after a player has been taking too long to complete a level. Their flat shape and rapid movement can make Baiters difficult to shoot.
• Bomber: Bombers are boxed shape and leave stationary mines behind. The mines can't be destroyed and need to be avoided by the player.
• Pod: Pods contain numerous Swarmers which are released when the Pod is shot.
• Swarmer: Small opponents released when a Pod is shot; their small size and quick speed can make them difficult to shoot.
• Firebomber: Similar to the Bomber, Firebombers roam about the playfield and shoot fireballs at the player.
• Yllabian Space Guppie: Attacks the player in swarms.
• Phreds / Big Reds: Square shaped aliens which launch miniature versions of themselves to attack the player.
• Dynamos: Large, diamond shaped ships; pieces of the ship break off occasionally and will attack the player.

Points are earned in the game for shooting aliens. Bonus points are also awarded for saving humanoids that have been captured, catching a falling humanoid and safely carrying it to the bottom of the screen, and for each humanoid remaining at the end of a level. Bonus lives are earned for reaching certain score thresholds (the amount of points needed can vary depending on the version of the game and the game settings).