Alien Building

Whereas human bases generally have the same structure and organization through all three stages, the diversity in alien building capabilities across stages means that alien bases must change dramatically throughout the course of a game, if the alien team is to successfully repel human attackers. Below is a stage-by-stage building guide for aliens.

Overview
Alien base defenses kill relatively few humans. Rather, they are intended to make an area of the map uncomfortable for human life, to distract, to draw fire, and to delay human attackers from reaching the important structures. A dispersed base is more important for aliens than for humans because humans have area effect weapons (flamethrower, grenade, Lucifer Cannon) that can attack multiple structures at once if they are clustered closely together. It is simply a waste of time to build 5 acid tubes on the ground near each other since a single grenade will eliminate them all at once. Eggs should never be clustered together. Make humans fire at each structure separately.

Human Threats
At stage 1, the painsaw suicide attack is a serious threat. One or more humans wielding painsaws can eliminate the Overmind and any ground eggs they can reach in a few seconds. Acid tubes rarely deal damage quickly enough to kill these suicide rushers. Accordingly, it is best to BLOCK humans from reaching the Overmind if at all possible.

At stage 2, the humans acquire pulse rifles, which can eliminate alien structures in line of sight rather quickly. However, aliens acquire the ability to place many structures on ceilings, out of reach of painsaw rushers.

At stage 3, humans acquire the Lucifer Cannon, which can kill most alien structures in a single shot.

Alien Base Building - Stage One
Aliens are limited to a very simple base structure in stage one, with only eggs, barricades, and acid tubes as potential accompaniment for the Overmind. At this stage, alien structures would be unable to repel a good human attack without support from defending aliens.

When building (“granging”), view your acid tubes as expendable, easily replaceable distractions that will delay a human advance long enough for your fighting teammates to do the serious damage. It's often advantageous to place a forward egg, surrounded by a few acid tubes, to surprise scouting humans and possibly drain them below 97 HP so they are vulnerable to death from one dretch headbite.

Although Overmind moves are usually not practical during stage one because of a likely early human attack, you can protect your overmind by making sure it can't be attacked from an angle where the attacker would be shielded from larger aliens. If necessary, place tubes and eggs near the Overmind to make nearby corners inaccessible to sneaky humans.

Barricades can be useful to block painsaw rushers from reaching the Overmind, assuming there is a suitable chokepoint available (in ATCS, this is the ramp up to the Overmind area). Barricades are not needed to block enemy fire at stage 1, since the available human weapons (mostly rifles) do not dispense damage fast enough to kill the Overmind in most cases.

In stage one, standard grangers can achieve wallwalk-like movement with the help of a friendly dretch. Advise the dretch to use wallwalk to cling to the very bottom of a wall. Then, jump on top of the dretch, using it as a platform. Once you are on top of the dretch, advise it to advance up the wall. Each time you jump with your granger while on top of the “dretch elevator,” you will move a little higher. This technique makes it possible to build in some hard-to-reach areas while still in stage one.

Alien base Building - Stage Two
The largest gains that the aliens make by achieving stage two are a wide array of powerful structures and the potential to upgrade to advanced granger for more hit points, maneuverability, and most importantly, the ability to easily build on walls and ceilings. It is very important for aliens to take advantage of these new capabilities by totally reworking their base immediately upon reaching stage two.

First on the agenda after evolving to advanced granger should be constructing a booster to help your team do more damage and regenerate faster. Place the booster where it can't easily be shot from beyond the range of your base defenses, but is easily accessible to aliens of all sizes. Do not bury the booster deep in your base where aliens can't reach it - it is more useful the closer to the humans it is! If your team is applying enough offensive pressure to keep the humans in their base, you might want to build the booster at a small forward outpost so it is easier for attacking aliens to use. In all cases, it is helpful to let your teammates know where the booster will be and encourage them to use it.

Next, begin using your wallwalk ability to move base structures from the floor, where they are vulnerable to saw rushes and grenades, to walls and ceilings where they can survive longer and also do more damage. Eggs should be placed safely out of common human lines of fire from doors and vents, but close enough to these openings that they can provide creep to sustain base defenses. Keep in mind that an egg's hitbox (the portion of a structure that must be hit for it to take damage) is at its base, so, for example, an egg in a groove on the ceiling would be very difficult to destroy even if it protrudes out of the groove.

Deconstruct some of your acid tubes to free up BP for trappers, arguably the coolest and most powerful structure available in Tremulous. Trappers are extremely deadly when paired with either defending aliens or acid tubes, so you should decide upon a tube-to-trapper ratio accordingly. If you are in a large game with lots of aliens to defend, you can replace every acid tube in your base with a trapper and count on your teammates to deal out damage to trapped humans. In smaller games, it is smart to leave a few acid tubes around, in case there are no aliens in your base to take down trapped humans.

Trapper placement is an art in itself, and if you master it your team can repel even the strongest human pushes. Trappers freeze humans by firing a projectile, but their aim is not very excellent. A trapper can only target humans that are within a conic area extending outwards from the trapper's base. Think of the trapper as creating a tripwire pointing in the direction that the trapper is pointing. With this in mind, it is essential to always place trappers so that they will be perpendicular to human paths - ideally, on a wall facing a nearby door, or on the ceiling above the door, facing downwards. The “floortrapper,” a trapper on the floor, will not affect any human unless he literally stands on it, and should therefore never be built. (Disagreement: although the floor trapper is scorned by players, it does work - humans MUST destroy it before proceeding past it - and so it could be useful.) Trappers have considerable range, so it is possible to place them far enough away from the entrance that they will be protected from splash damage from lucifer cannon fire and grenades launched from outside, but still be able to trap incoming humans. Basically, try to arrange your trappers so that humans cannot destroy them without getting trapped first. Well-placed trappers frustrate humans and make your teammates' job much easier.

Alien Base Building - Stage Three
After you are done setting up your base in stage two, you shouldn't need to make many changes. Aliens only have access to two new buildings in stage three, and neither is very remarkable.

Inexperienced builders assume that because hives cost more BP and are available later in the game, they must be superior to trappers and acid tubes. This is simply incorrect. Although hives can output more damage than acid tubes, they can only target one human at a time and are therefore very ineffective against any group of human attackers. Trappers and acid tubes can slow and damage many attackers simultaneously, making them the better choice. Hives are somewhat suited for taking down jetpackers that may venture into your base, because their insect swarms have a slightly longer range than acid tubes. However, if your trapper and tube defenses are adequate, jetpackers should not even be able to enter your base in the first place. Hives seem underpowered for their build cost.

The hovel is somewhat of a joke in Tremulous, as, in the event of a large human attack, grangers are usually more likely to survive by scurrying around on the ceiling, rather than hiding inside a conspicuous building. The hovel's true merit is that it costs zero build points, and so is essentially just a free barricade you can use to shield your overmind or eggs from fire or prevent common routes for luci jumpers (humans who fire a charged lucifer cannon shot at their feet to reach a platform). The hovel can also be used to block human approaches, replacing the barricade for zero bp.

Once in stage three, the granger's main role is to maintain the existing base until sudden death.

Miscellaneous Tips

 * Aliens can build faster and more expansively than humans. If you sense your base is about to be overrun, try to sneak out of your base and plant some eggs to prolong the game. Often, a struggling alien team can keep humans on an “egghunt” long enough to reach stage 3 and turn the game around.
 * On larger maps, it is often useful to keep at least one hidden egg outside of your base, as a backup in the event of a strong human attack.
 * Be very careful when deconstructing eggs, as alien structures cannot survive outside of the creep, area near eggs and the overmind. If you remove an egg that is providing creep for any of your structures, they will explode shortly afterwards.
 * The only situation in which an advanced granger should attack is when a human is frozen by a trapper, and completely defenseless. Humans will target grangers for easy credits, so the best thing to do is avoid combat altogether.

Stage One

 * Overmind
 * Eggs
 * Acid Tubes
 * Barricades

Stage Two

 * Trappers
 * Boosters

Stage Three

 * Hives
 * Hovels