The Wars of Marcus Aurelius: Rome 170-180CE is a solitaire only game that uses cards similarly to a CDG to simulate the strategic level struggle of the Romans led by Marcus Aurelius to stave off the invasions of Germanic tribes and Sarmatian raiders as they encroach on Roman territory across the Danube River.
Here are links to a series of Action Point posts on the various aspects of the game:
If you like a good solitaire game, with great components, that plays in about an hour and is very challenging (code for hard to win), then this one is for you. I fully endorse this game and give it my highest marks for a solo experience.
In this playthrough, I get lucky and actually win the game by being very aggressive. Aggression is the key and you must keep up the pressure to win. I take responsibility for any mistakes made in the gameplay and want to emphatically state that no Romans or innocents animals were harmed in the production.