The Mian game:

First person shooter

Uses the new proprietary 3-D PAIN Engine

All weapons come in pairs, with a primary and secondary fire

Advanced AI coding will simulate group behaviours

For 1 or more players over LAN or Internet

The Expansion:

10 entirely new, diverse and bigger levels no texture ever reused, each level is entirely unique

4 new weapons, grouped in pairs, including a flamethrower/semi-machine gun

2 new multiplayer modes, including a hellish mutation of Capture the Flag

New multiplayer maps

Improved game engine: improved visual effects, updated network prediction code

Redesign entirely the single player campaign, or create new MP maps with the full set of editing/modding tools provided with the add-on