How do you purchase upgrades on Steam?

[euroq]

I'm a little confused, I was looking for the sequels or add-on packs or whatever on Steam. I did a search for "Defense Grid" and the results showed me the original game, which I own, and also 4 map packs. (Resurgence) So I take it I can buy these 4 map packs and run Defense Grid with new maps, but isn't there another add-on with a different name?

[euroq]

I don't see Borderlands on Steam.

[jeff]

If you buy the game on Steam, it automatically downloads the free 4 map expansion called Borderlands.*





Jeff