So far, I've just played the game itself which I downloaded for $19.99. If you want to try it, a link is below:
The programmers have come out with two expansions for the game that I'm going to purchase shortly. You can buy the pair for $19.95.
You can also buy all three at once, but I wouldn't suggest that. First try the original game. Then if you like it, buy the expansion packs later. My twelve-year-old son really enjoys the game too and has reached the point he can give me a good game.
I like the game so much, I made the programming company (Stardock) my first affiliate for this website. You can use their services to buy a host of games and download them directly to your PC. The best part is that they remember what you bought, so if your hard drive crashes (or if you just replace your PC), you can then download all the games you already bought at no additional cost.