Natural Selection/Marine structures

A team without structures to provide them with various benefits is going to lose very quickly. These are essential to your team, and you should guard them well.

Resource Tower
Resource Towers are some of the most important buildings for both sides, and should be protected well. Each tower gathers one resource point every few seconds. A team without resources will be killed quickly.

Electricity is so so. I'm not that big of a fan of it. It can kill Skulks with ease, but once the 2nd hive goes up, Gorges can easilly Bile Bomb it to death. Fades can Slash, back off, and heal til its dead as well. I would only recommend Electricity if you have a node is some far off corner you don't think will be discovered for a bit, and is harder to access with something other than a Skulk or Lerk. So, for the most part, hardly ever.

Infantry Portal
Probably the most important building. These little guys revive you when you die. And you will die. A team without an Infantry Portal, well, won't be able to respawn. Guard these buildings the closest of them all.

Armory
This building dispenses ammo for whatever gun you have equipped. Your team will spend a lot of time around this one. Not defending it, but "humping" it. Thats not my word, its the slang NS Players use to refer to players getting ammo. Usually way to much ammo. You do not need 50 | 250 ammo for your LMG. Its likely you'll die before you use it all. 175 is usually what I get, and I very rarely run out of ammo. Make sure you do get maximum ammo for all the dropped weapons, especially the HMG and Grenade Launcher, as they chew through it very fast. In NS 1.04, you used to move slower depening on how much ammo you had - im not sure this is still in 2.0.

Command Chair
Lets Commanders Command. This has the highest HP of all Marine buildings, so it should take a while to kill. If the Command Chair is about to be destroyed, build another ASAP! Otherwise, you're pretty much screwed.

A little known bug about the Command Chair is that upon entering, you get full HP. If your playing on a LAN and can communicate well with players, this will let them heal without wasting res on med packs. Don't try it in public servers though, as likely some idiot will get in and not get out.

Turret Factory
Lets turrets be constructed. Turrets can only be placed around the Turret Factory. Also, if the turret factory is destroyed, all turrets in its radius will be deactivated - not good! Because of that, put this guys along walls and corners to reduce the amount of angles it can be attacked at. Also, use turrets to cover all exposed sides, as the Turret Factory will block fire from the turrets. The last thing you want is a huge turret farm taken down by 1 Skulk who was able to find a blind spot on the Turret Factory. Because of this, I DO recommend Electrifying them when possible. After all, a Skulk could keep chomping on 1 turret to make a blindspot.

Upgrading to the Advanced Turret Factory allows siege Cannons to be built. For details on these beasts, read the appropriate section.

Turret
Turrets. They shoot at people. Though these turrets are pretty weak, they can usually take down an Alien before he does any significant damage to one. Provided you mass them, as you should. Use these to defend your base, res nodes, hives, and any other location you deem to be important.

Also, Turrets now do half damage to Oni.

Siege Cannon
Oh ho... I love these guys so much. These behemoths shoot at enemy structues - even through walls! Once set up, they take a second to acquire their target, and then they let loose. Of course, as soon as an enemy hears the shot of a siege cannon, they'll be on it like flies on honey. Make sure while the Turret Factory is upgrading and the siege is doing its thing to place normal turrets to help defend. A phase gate to base might be a good idea too for quick reinforcements. For best results, deploy 2 or 3 of these at a time, since thats, well, 2 to 3 times less time you spend in enemy territory. A single siege Cannon in your base can help as well, to destroy any healing or cloaking stations the Aliens set up nearby.

siege Cannons do 165 damage per shot, and have a range of about 1 screen on the command interface. Theres nothing worse that building a turret factory, build up turrets, plop down a siege, and you learn it can't reach. So make sure you'll be in range. Also, these Turrets do not shoot at players. They can however, hurt people close to the impact, including Marines.

Observatory
These handy little buildings have a lot of different uses. First of all, they decloak any Aliens within their radius. Always have one at your base, and any other important installation you have.

They also generate energy, which can be used for a Scanner Sweep. This handy little device sends out a blue "shockwave" that allows the Commander to see everything in the radius of the affected area. It also decloaks everything in the area for 10 seconds. If your Marines are heading into an unfarmiliar area, please, please, PLEASE use Scanner Sweep. Very few Comms do this, and oftentimes Marines get ambushed by cloaking aliens or Offense Chambers. Having more than 1 Observatory will regnerate energy faster, and thus allow you to scanner sweep more often.

A very vital function Observatories have is the distress beacon. For 15 resources, you can bring all Marines back from death almost immediately. This is vital if your base is being beaten to bits, and your only respawning people 1 or 2 at a time.

Observatories have access to the Motion Tracking Upgrade. For a very expensive 45 resources, this is a fantastic one to get, albeit expensive. Any aliens that move will get a blue circle around them, so this could be the equivalent of a wallhack.

Finally, Phase Gate Tech lets you build Phase Gates. Fascinating. ^_^

Arms Lab
A very vital building. Each upgrade to your guns lets them hit 10% harder than they originally did. Each armor upgrade increases your damage resistance and raises your maximum armor by 20. Every once in a while, when you can spare some resources, be sure to upgrade something. Most people go with weapon upgrades first, since they also power up turrets. I prefer armor first though, as it lets Marines take another Skulk bite than normal. Either way, you should probably alternate back and forth between the 2. If its destroyed, you lose all your upgrades.

Prototype Lab
Allows you to research these 2 technologies and deploy them around the Prototype Lab. Thats really all it does. Read the Jetpack and Heavy Armor sections for more details.

Phase Gate
These act as warp portals around the map. So if you put a Phase Gate in your base, and one in a hive, pressing use on the Phase Gate will warp you between them. You can have as many as you want, but dont go overboard, since you'll just cycle through all the gates you've placed until you finally get to the right spot. By that time, it may be dead. 2 or 3 is all you'll need, most likely. Recycle phase gates you don't use anymore to shorten trip time.