Free Introductory Mac Strategy Games?

Ever since my Mom got her new Macbook, she’s been a total flash game addict. Word games, match-the-gem games, silly “get the ball in the bucket” games – the whole gamut.
She’s a gamer, but a gamer that’s never been exposed to games beyond these simple mindless toys. Granted, some of them are sort of interesting and fun, but there’s a whole world that she’s never seen.
Now me? I’m into Starcraft, and Civilization, and Eve, and all these epic immersive things. But for someone who has never played the basics, these are completely daunting and will more likely scare her off than intrigue her.
So where do you find the middle ground?
I’m looking for basic, introductory games for the Mac that are free (or really close to free), that should have a basic plot line (even if it’s trivial), and some way of advancing through the game.
We tried FreeCiv, but that’s targeted at people who already grok Civilization, so that’s not going to work. Something simpler than that, along the lines of Master of Orion (the original), Spaceward Ho, etc etc. At some point she tried the original SimCity but that almost ate her brain, and she deleted it. However, this same woman is one of the best players I’ve ever seen at… believe it or not… Crystal Quest. Granted, that’s also a mindless “keep shooting” game, but it takes some serious chops for the upper levels.
So, dear readers, what would you suggest? It can be flash based, or downloadable, needs to run on the Mac, and should have a very basic level of introduction, particularly to turn based gameplay where there’s regular advancement. The first one I’ve come across that comes even remotely close is TradeWinds, a trading game set in Arabia. Very simple gameplay, entertaining, and has a plotline of sorts.
Any others?
(Note – I’ve had reports of people having problems posting comments to the blog. If you have a problem, please send mail to me ( dbs@homeport.org ) and I’ll look into it!)