Base defence is set as the first mission in revision 2736, for testing. Please test!
I really enjoyed it. There were no civilians, and only 9 aliens, but it was a lot of fun.
It is bad that aliens and soldiers can't move to where there are no buildings. At least a fence is needed to make this somewhat justifiable. Perhaps enable all base squares that are adjacent (even diagonally) with the base squares and put a fence on them. Perhaps also a few alien spawn points there (on the inner side of the fence).
Very nice play. I played it to the end. Sometimes, outside the Entrance building, camera does not switch to the surface level when aliens are shooting (outsiede the wall opposite to Entrance door). Also the top platform of the stairs seems to belong to the cellar level.
To make base defense even more interesting when it's repeated, one random alien should spawn in a random room, or the aliens should have a small chance to bash doors with each shot at them, with lots of noise, to attract player's attention. Also alien spawn points should be outside all buildings, so that they storm the Power Plant doors from many directions. There should be no alien spawn points around or inside the Power Plant and there should be especially many around and inside the Entrance, and slightly less for Dropship Hangar, Interceptor Hangar, Radar, UFO Hangar. Civilian spawn points should be only inside buildings and not in those that many aliens spawn in. There should also be some things for hiding behind on top of Storage building and perhaps elsewhere on top of buildings.