X-COM Base Terrain
Eventually the aliens will find their way back to one of your bases and attempt to overrun it. This at least should be familiar territory: you've laid it out yourself, and have been working in it for months on end. Unlike other areas, whose terrain you will be laying eyes on for the first time at the start of the battle, your troops know the layout of the base right from the beginning. This is the only non-random terrain in the game-- the layout always reflects the base plan.
The smart Commander has laid out the base with defendability in mind. The surface access points-- the lift and the hangars-- have been grouped together, and all isolated from the rest of the base. Hopefully there is only one choke point between the surface access and the base, unlike the example picture here.
Remember all those times your troops were ambushed in farmhouses, or had to rush the hatch of a UFO crawling with aliens? Now's the time for payback. With a good base layout, you should have enough time to set up good ambushes. Hide behind doors and pop out of them to engage the enemy. Make sure the choke-points are covered with every dirty trick you can think of. They should soon be choked with alien corpses.
See Xcom_and_Alien_Bases#XCom_Base for a full set of maps.
- Your troops will begin the battle scattered around the base, concentrated in the general stores and living quarters. Tanks will be principly in the general stores, as will unattended weapons.
- Don't soil your own nest. Some caution must be taken to avoid utterly destroying base sections, and losing them permanently. While any section can withstand one blaster hit, multiple blaster and explosive hits in the same section should be avoided.
- Hangars, access lifts, general stores, alien containment chambers and living quarters are hardened against attack, and cannot be destroyed.
- That said, don't be afraid to blow a wall or two down to protect your base. Blasting the doors off the otherwise-indestructable access lift is a good way to deny the aliens cover.
- the 80-item limit can be especially painful for a base that's stuffed with extra weapons and alien artifacts.
- Many modules have lots of smaller rooms and HWP closets. These cubby holes are good places to run for cover in between turns, and can sometimes provide your team with one chance of surviving a blaster bomb attack.
- Soldiers with motion scanners can do well by staying in the upper levels to scan for movement along the lower corridors.