Fun game, I want to see more.
The glitches that I am aware of people already have mentioned, so I won't waste time on those. I found it fun, a little easy sometimes (except for the twilight level, that one took a few tries). The endurance level is too easy as people have mentioned. Set it up so that failure you probably going to happen eventually (maybe give the computer like twice the building area so unless you have some really good strategy down you will eventually be overwhelmed.
I think a sandbox mode would be really nice too. Where you can set up the starting area sizes, initial roads (the ones your factories can build to), starting money for computer and person (make it so you can give one or the other the advantage). Even have it set up where you can build the factories for the sides before starting (I am just curious what would happen if I went up against 5 fully upgraded tank factories with just a swarm of fast producing weak guys or something like that). Just so you can experiment around with different battle types. Even choose what weather happens, etc. etc.
Overall a fun game and well done. There aren't many games I can think of that work exactly like this, some similarities, but enough tweeks to make it a new game. I hope to see more.