Aside from the single-player campaign, Liberation also packs in superfast, six-player matches across six different levels. We've only played the deathmatch mode so far, although we're told the game will feature team deathmatch, assault and capture-the-flag modes as well. Not that it really needs them; the action with a full six players was some of the most fun we've ever had with a non-Bomberman multiplayer game.
If you're looking for something slightly more sedate, Liberation will also feature a cooperative campaign mode for two players. Whether you're playing co-op or competitive, however, you'll have to do it in the same room; when the game launches on Halloween, it'll only feature ad-hoc play.
The good news is, that'll change real soon. Shortly after launch, publisher Sony plans to offer a few free downloads from the game's official site, one of which will add online Infrastructure play to the game. Another of the unprecedented downloads will be a full new chapter for the game's campaign mode, adding four full missions and a few new multiplayer levels to the mix.
While it's still a ways from release, Killzone: Liberation is arguably the most promising PSP shooter we've seen yet. It's fast, addictive and somehow manages plenty of depth with relatively simple controls. Unless it's somehow messed up before launch, this is something to look forward to.