A huge update for Sid Meier's Civilization V launched on Steam yesterday, bringing the long-awaited Hot Seat multiplayer mode along with heaps of changes and updates.

Hot Seat multiplayer lets several players compete in front of the same computer, taking their turns, well, in turn. The changelog also notes, "While play-by-email is not yet implemented, we did include an in-between turn saving option for those that want to play via email."

Complaints about a lack of difficulty have been addressed with pacing tweaks. "Expect to have more of a challenge managing your empire at higher difficulty levels than you did before," the notes state. "Consider dropping a difficulty level if you have problems."

The patch also brings scores of tweaks, changes and fixes. On the AI front, you can expect computer-controlled nations to create better army compositions, behave more sensibly in diplomatic matters, pursue "back-up" victory paths, and properly execute late-game amphibious invasions if land-bound.

Units, buildings, tech, and nations have been all shook up with dozens of balance tweaks. If you load an old save into the new version, the notes warn, "the balance pass may make your existing happiness lower than expected when loading into your existing save post-patch." Plus your once-brilliant army might be a bit rubbish now, of course.

Do check out the huge full patch notes to see exactly what's new.