Stargate is the sequel to Defender, both manufactured by Williams Electronics and created by arcade legend Eugene Jarvis (who is only slightly less legendary a game designer than Ed Logg), and is one the most hideously difficult arcade games ever made.
The basic play was the same as Defender. The player controlled a spaceship in a side-scrolling world five times larger than that represented on the screen.
Defender had six types of enemies, Landers, Mutants, Pods, Swarmers, Bombers and Baiters. Stargate had five more, and three types of "named shots": Firebombers (and Firebombs), Dynamos (and Space Hums), Big Reds and Phreds (and Munchies), and the oddly named Yllabian Space Guppies. (Try spelling Yllab backwards.) All the player's "friends" from Defender were back as well, with an updated look.
Lander, and his Lander friends, scour the world looking for humanoids, who the player tries to defend. If one succeeds in abducting one and can carry it to the top of the screen, it turns into a...
Mutant, who is much more aggressive than his larval state, fires very rapidly and relentlessly tracks the player. Furthermore, if at any time all ten humanoids are killed or turned into mutants, the world blows up and all remaining Landers become Mutants. All waves become "Deep Space" waves until the wave number becomes a multiple of five (operator adjustable), at which time all lost humanoids are replenished and the planet is restored, if previously destroyed. While all this is going on, the player must contend with...
Pods, which are worth 1,000 points and do not attack, but must be destroyed and when hit release many...
Swarmers, which are not only almost as aggressive as Mutants but are also much harder to hit. Also infesting later levels are...
Bombers, which don't fire or chase the player but instead follow a fixed path through the world, leaving a trail of bombs behind it, which don't move but tend to get in the way. The last enemy in Defender is the...
Baiter, an extremely dangerous foe which functions as a kind of timer. If the player takes too long in clearing a wave, Baiters start to appear nearby, and keep appearing, more and more often, until all other enemies are destroyed. (Baiters themselves, though worth 200 points apiece, are the only enemies that need not be destroyed to clear a wave.)
In Stargate, the original enemies are joined by
Firebombers, which fire extremely rapid shots called Firebombs left and right. These shots can be destroyed by your ship's laser, but since you can only really shoot a Firebomb (or a Firebomber) when you're on its plane, this is a very dangerous tactic. Firebombers, thus, are prime targets for a Smart Bomb or for engaging with Inviso turned on. Wave ten is the Firebomber Showdown.
Dynamos are small diamond-shaped craft which slowly float around the world, launching their tiny guided progeny, Space Hums at you when close by. Neither Dynamos nor Space Hums are actually very difficult, and can usually be regarded as easy points. But try not to underestimate them, as even Landers can be dangerous in certain circumstances.
Yllabian Space Guppies are the only new enemy type that does not fire "shootable" bullets, they look different, but they must be dodged or Invisoed through just like the little white dots launched by the original aliens. They are called Space Guppies because they tend to travel in schools, and indeed may be an early example of a "flocking" behavior in a videogame. (For a more recent example, check out the fish in the pond outside the castle in Super Mario 64.) They tend to travel most quickly horizontally, and to stick to their school, but otherwise they move not unlike a slower version of the Swarmer. They make "passes" at the player, diving in launching many shots, then continuing past a short distance before turning around for another run. Their bullets also travel horizonally. Wave five is the Yllabian Dogfight.
Big Reds and Phreds are boxy Pac-Man like monsters which fly after you like Swarmers. And like Baiters, they appear when you take to long in clearing a wave, and need not be destroyed to proceed to the next level. Also like Baiters, they appear more and more frequently until the level is finished. (Though the game tends to give you a break when you lose a ship.) Phreds fire Munchies, which are much smaller, faster versions of their parent craft. If you stick around too long they will eventually belch forth a huge number of these tykes, to which a planet explosion and the ensuing rush of Mutants is almost preferable.
The difficulty of Defender and Stargate lie not in the sheer number of foes, but by the fact that they all have their own unique way of defeating the player. Arguably, Mutants are worse than Landers, but if you're successful at protecting the humanoids they may never appear. Pods can be easily dealt with by shooting them, then Smart Bombing the resulting Swarmers, but Smart Bombs are in short supply. Bombers are stupid, but in later waves drop many bombs, and become a major nuisance in that manner. The new Stargate enemies each are lethal in narrowly-defined ways. You are almost safe if you rest directly above or below a Firebomber, but you're going to have to do something about it to complete the wave before the Baiters, Big Reds and Phreds show up. Yllabian Space Guppies travel in packs, so you can take care of many with one Smart Bomb or with minimal Inviso, but again, these are both limited resources. Dynamos are a cinch if you focus your attention on them, but so much is happening at any given time between the screen and the scanner that their relative ease can cause you to underestimate them.
In Defender, the weapon of choice was the mighty Smart Bomb, of which the player began with three and gained another one every time he earned an extra life (once per 10,000 points on default settings). Smart Bombs destroy all enemies on the current screen, making them a wonderful panic button. Added to Stargate was the Inviso button. Additional units of Inviso time (which is on only while the button is pressed) are earned at the same score levels as ships and Smart Bombs. Inviso makes your ship both invisible and invincible. (Why not just make the ship invincible, I have no clue.) Both games, directly copying Asteroids, also have a Hyperspace button, which teleports the player to a random location on the planet, but sometimes caused the player to explode, at times because his ship materialized inside an enemy, but also sometimes just because. Stargate has a better solution in its eponymous Stargate, a wormhole at a fixed location in the planet's sky which can be flown into, and never kills for no reason (but can still be dangerous if an enemy is nearby where the player rematerializes). The Stargate usually just takes the player to the opposite side of the planet, but if a humanoid is being abducted, the Stargate will always set the ship up for a rescue, not only placing the player about half a screen length from the kidnapping, but also putting him at a reasonable height from which to stop it! If the player is carrying four humanoids, and has not yet passed wave nine (operator adjustable), flying into the Stargate will cause the player to "warp past" four levels, and award the player 2,000 points for every humanoid alive at the time. This is the first recorded instance of a "warp," or level skip, beating Super Mario Bros. by several years.
Popular opinion is that Stargate is an even harder game than Defender. I don't buy it, I average about twice as many points in the sequel than the original. While there are more, and more varied, foes, killing them awards the player more points, and thus more frequent extra lives and smart bombs in what is essentially a game of attrition where you're always losing lives, but it's okay as long as you gain them faster. The player also has a new weapon at his disposal, the Inviso shield/cloaking device. The player also has the Stargate itself to help out, the option to "warp ahead" levels for a large score bonus, and must defend humanoids for only four out of five waves. Each wave that is a multiple of five is a "special wave," with no humanoids and a special theme, which features a reduced mix of foes focusing on one particular type. Since humanoids aren't even present in these levels, and are refreshed afterwards, the chances of Mutant Apocalypse are similarly reduced.
Personal best score on Stargate (default difficulty, Dreamcast emulated version): a little over 80,000.
Twin Galaxies record (difficulty 9, start units 5): 71,473,400, earned by Roger Mangum.
It should be noted that the thing that made Defender and Stargate so soul-crushingly hard was not that they would kill the player without warning, or give the player impossible situations unless more cash is inserted, like in so many modern arcade games. They did not. On a game where average scores are likely well under 50,000, the highest recorded scores are over ten million. They are hard because on higher levels, the player needs almost superhuman reflexes and a damn fine strategy to survive for long. A difficult challenge indeed, but not insurmountable. I ask, which is harder, a game in which a tiny fraction of people can play for hours, but most burn out in under a minute, or a game which gives the player impossible situations every three minutes that can only be overcome by bribery? That is no game – it is merely a ride, a Ferris Wheel for the eyes and hands.
NOTE: In one of the most shameful debasings of a great minor work in favor of a mindless big-budget hack project, WMS was apparently forced to retroactively change the name of Stargate to "Defender II" upon the release of the movie Stargate, which has already been forgotten by most people with lives. (Hey, I heard that sarcastic remark you made about people writing two pages about a videogame!)