There was a game from a while ago on kongregate, that I cannot remember the title of for the life of me. I don’t know if it’s still around, but if it is, I’d love to play it again.
It was a tower defense, but everything was in the form of civil war soldiers. I remember there being riflemen, barricades to set up, and different forms of infantry units that would serve as the “towers” of a normal TDF game. The highest power weapon was the first form of the gatling gun, I think.