Including some code cleanup, I fixed the fog-of-war so that it moves with a unit as it moves. It’s not very important, but it was bugging me. I realized that movement of multiple units at the same time is also broken, which I haven’t looked at yet.

The next thing was starting to implement enemies. The spawning is basic now: enemies spawn close to an enemy controlled core, and they don’t do anything. Making them move, attack and be attackable is the next step (or next few steps).
In future, I want them to spawn more intelligently. Not under safe areas, but near the edges. I’m not sure how to handle making them spawn if large segments of the map are safe, but probably still at the edges.

I’m not sure what the mechanic to take over enemy controlled cores will be. I suspect it will a control network connection and some sort of countdown timer when many enemies rush the core to try to stop the takeover.