->''"The Time Bomb Is Set."''
-->-- '''Announcer'''


''Alien Syndrome'' is a 1987 arcade game released by {{Sega}}. One of the earliest examples of an overhead action shooter, the game revolves around two alien exterminators named Ricky and Mary (allowing for 2-player co-op play) as they're sent on a mission to rescue the inhabitants of a space colony infested by strange creatures. Their objective is to rescue the 16 hostages in each of the spaceships that form the colony before time runs out and then proceed to the exit in order to fight one of the alien bosses. There are a total of seven stages, with the final stage being a single boss battle against the alien mastermind.

''Alien Syndrome'' was ported to a variety of 8-bit platforms at the time, including Sega's very own MasterSystem and GameGear, as well as a Famicom/NES port released by Sunsoft in Japan and Tengen in the U.S. There were also two updated remakes as well: a 2004 version by [=3D Ages=] released for the [=PS2=] (as part of the ''Sega Classics Collection'' in the U.S.) and a 2007 version by Totally Games released for the Wii and PSP.

!!This game provides examples of:

* AliensAreBastards: Though of the generic ExcusePlot kind, mostly done for the sake of gameplay.
* BossDissonance: Varies based on port. Common points of reference:
** The arcade version can have either easy or hard bosses, but they do pose a threat.
** The Commodore 64 port tends to have bosses that are harder than the rest of the level. The first boss second stage, for example, is only vulnerable for a few seconds as it makes a quick-moving attack, and is more durable than the arcade counterpart.
** The Commodore Amiga port tends to have bosses that are easier than the rest of the level, simply because of the laser and an ability to exploit known behavior. However, the final super alien is technically harder as you're under a strict time limit under this port.
* BossInMooksClothing: The enemy spawners. The take quite a bit of damage, and will be a serious drag on your race against the timer, should you choose to kill them.
* EliteMooks: The arcade version had these, though most other versions did not.
* ExcusePlot: Save your comrades, defeat the aliens, and not much else.
* FrickinLaserBeams: One of the weapons available to the player. Normally just a projectile speed and range upgrade, but the Amiga version makes it rapid-fire and therefore has it do the most damage per second.
* HitboxDissonance: Like all early games, it has some form of this. However is it particularly noticeable in the NES version, where even normal baddies sometimes have an InstantDeathRadius due to this. It's worth noting that this also makes them easier to kill.
* InstantDeathRadius:
** In most cases, this is due more to HitboxDissonance than deliberate design.
** In the Commodore 64 port, the super alien attack in Round 7 is almost screenwide and requires you to move in and out of range because it is now difficult to dodge.
* MookMaker: The ones in this game overlap with BossInMooksClothing above.
* PowerUp: Gun upgrades were not necessarly powerful than your default one, but may have better range, rate of fire or speed. There are also two robots that you can collect and have them follow. There is also a powerup letdown that changes your current weapon back to the basic shot.
* RespawningEnemies: Two types, both the types that spawn from a SpawnPoint, and the types who respawn from scrolling back and forth on their spot.
* ShoutOut: Many versions feature an enemy resembling [[Franchise/{{Alien}} Xenomorphs]].
* TacticalSuicideBoss: The first alien boss can survive simply by not using one of it's attack, or by not attacking during it's second stage. The Commodore 64 port makes this more obvious, as the action making it vulnerable doesn't do an attack, and where it could technically wait the player out on the second stage of the battle.
* TimedMission: Each mission starts by setting a time bomb that detonates after 150 seconds (or the time specified by the port or arcade operator). The timer is extended by 30 seconds upon reaching the boss. If the time runs out, you lose a life and restart the level.
** The Commodore Amiga port causes a NonStandardGameOver if you run out of time.
* VacuumMouth: The vacuum is actually six air clouds that spiral in to the mouth, and dodging them means you aren't sucked in. Compared to the arcade version, the Commodore 64 version makes it hard to dodge and requires moving in and out, while the Amiga version makes it ridiculously easy to dodge (where the threat is on the timer and not the alien.)
* VideoGameFlamethrowersSuck: The flamethrower is short range, where the flame itself disappears when it strikes an enemy. It works like the other weapons, where it fires more often if you rapidly tap the button. On the other hand, there is a fireball which is a long range version of the shot.