About Aliens versus Predator: Extinction

All I can say about this game is that it would've been awesome without the Predators, with twice as long vision range and if completing the optional objectives was actually useful. Others beside me have expressed their desire for multiplayer, too, though I personally would've loved a custom scenarios.

Basic description:
There's a campaign for each faction: colonial marines, predator clan and the xenomorph hive. Each campaign has 7 missions with varying goals, though each requires killing of something before the day is done (even if the actual goal isn't to kill anyone). Personally I found the xenomorph campaign to be easiest and the most enjoyable, wishing there was much more of it. The marines came second though with them the gameplay is much more difficult since their extrasensory detector does not allow attacking outside the sight radius. Predator campaign is the hardest, mostly because you control only so few characters and they some specialized units require specialized units from you that normally aren't very useful. Usually at these times you'd want your other units to stay the hell away from the combat, but they have inborn suicidal tendencies which prevent this (although you could tell them not to move, but that eliminates most of their usefulness in pretty much every other situation). More powerful units are unlocked as each campaign progresses.

Faction specifics:
Marines have only ranged weapons, some only useful at close range - such as the flamethrower marine. Marines have only motion detector to see outside their visibility range and therefore rely on sending synthetics to increase it (synthetics also are the only ones to carry the detector). Without this the marines are severely disadvantaged due to their even naturally abysmal sight range and reliance on ranged weapons (kinda quirky for the purely ranged faction to have the worst sight). Some marine weapons have questionable effectiveness, such as the impact grenade launchers the regular pulse rifle marines get. Single alien warrior can survive 4+ hits from such and still be combat efficient. Marines are healed by the specialized medic who also removes special effects caused by predators and xenomorphs. Synthetics and the sentry gun are the only ones that can dispel predator cloak. Marines gain miniscule amount of requisition points (credits) with each kill (20-50 or so), and they can additionally tap to power stations for additional though finite credit flow (usually 2000; compare the price of 350 of synthetic and you get the picture). Reinforcements are called in by a ComTech and they arrive at the nearest drop site, marked by a landing beacon (part of the level design, can't be designated by the player). If no ComTech survives, the player must do with what she has left as there's no way to order new troops or new ComTechs after that. Medics require another medic to heal themselves, so having two medics is a necessity. Marines are also limited that they can only bring 6 units to the mission with each call and have to wait for the dropship to arrive drop the new troops and leave before more can be ordered.

Predators have range of melee and ranged units. Heavy emphasis on cloaking and taking out any detectors employed by the opposition. With vision enhancements the effective sight radius is immense, making plasmacasters, disc throwers, and spear throwers immensively powerful. Unfortunately the AI knows your reliance on cloaking and spams detectors half the time, effectively nullifying any benefits it has in your use, due to their vast numbers, it isn't practical to kill them instead of the other units with actually damaging weapons. Predators require energy to keep the cloak active, which usually lasts for quite some time, but the energy regenerates extremely slowly. The same energy is used by the medical equipment each predator carries (they can heal only themselves). The center of operations for predators is the Shrine, a floating altar with a veritable weapons system and ability to rapidly self-repair. Predators have three global upgrades unlike the other factions, unlocking each of the three vision modes for detecting heat, electrical and predator signatures at extreme range. Unfortunately none of these seem to catch synthetics, making humans the most difficult opponent you face. A minuscule amount of requisition is gained with each kill, more is gained by extracting the skulls from the slain enemies (your enemies can destroy the corpses to prevent this, and some of your weapons totally annihilate the bodies, also preventing it). The Shrine works similarly to a ComTech in terms of its necessity. However, new troops arrive instantly by drop pods around the Shrine.

Xenomorphs effectively simulate the alien life cycle and have heavy emphasis on melee units. Xenomorphs have decent sight radius and additionally employ "spore vision". Spore vision works by marking any organic enemies so they're visible to the player at any range from henceforth, also eliminating any use of the predator cloak. The xenomorph lifecycle starts with the egg, which bursts open and sends a facehugger flying at the nearest enemy. This is rather unusual event, though. Without any other units, the facehugger would quickly seek prey and impregnate them with a chestburster. The chestburster rapidly emerges and evolves to one of the xenomorph breeds designated by the host organism. Runners and drones from animals, warriors from humans, predaliens from predators and so forth. The egg must be upgraded to Praetorian egg at cost of 300 points, which then gives birth to praetorian facehugger, a much larger and tougher one that can impregnate armed marine single handedly (regular facehuggers require a large group to accomplish it). This produces Praetorian xenomorph regardless of host creature, similar to drone and warrior but much tougher and powerful. The Praetorian also disperses spores. Praetorian can then be evolved into hive queen, the near-equivalent of CommTech and Shrine except it's effectively even more powerful version of the Praetorian. Unlike the other factions, the queen does not order new troops, instead, she lays eggs at steady pace (though this makes her immobile and unable to defend herself, the egg production can be ceased to change this, but growing a new egg sack costs some requisition points). The other xenomorphs are used to kill enemies, drones are especially important with their cystic upgrade as any creature infected with them creates more powerful xenomorphs (prefixed with cystic). Usually you want several drones to accompany your war parties to ensure as many as possible are infected with them. Almost all xenomorphs leave their victims alive although comatose. These comatose creatures can then be dragged back to the hive (gather command is especially useful for this) where the ready waiting facehuggers can safely impregnate the creatures. Human civilians and animals have a habit of respawning, so you usually have ready source for at least one breed of xenomorphs. There can be only one queen however, but if the queen is lost, as long as you have at least one egg, praetorian facehugger, or praetorian, a new one can be acquired as easily as your basic xenomorph breed. Xenomorphs also don't spend their points on acquiring new troops, only upgrades. Drones are unique also in the manner that they can spawn hive nodes that produce the spore vision, they also produce biogrowth in a small radius on which xenomorphs heal. Only Runner and PredAlien can heal outside of this. Since aliens need so little of the points for anything real, the player can and should spam the hive nodes to expand their early warning system, increase the number of locations where they can heal and generally to be a nuisance to the other factions. Note however, that the facehuggers slowly die outside of the alien biogrowth and generally have abysmal resilience to beatdown, making them only useful in large masses against mostly singular armed enemies, however, since they're free, they do provide some use.

Common to all factions are that upgrades are once per mission style instantaneous improvements to all units of certain type, usually costing 350 points on average (from range of about 200-600).