Having vowed to update the recently launched Steam for Mac digital distribution platform with more games every Wednesday, operator Valve has rolled out several new titles.

The theme of this week's offering is cross-platform multiplayer, with titles like Altitude and Killing Floor allowing both PC and Mac gamers to play against one another. To celebrate, Killing Floor is temporarily $13.39 (33% Off), Madballs is $4.99 (50% Off), and Altitude will receive a free multiplayer weekend alongside a $4.99 (50% Off) sale.

The update also brought several single-player games, with today's titles listed below:

• Altitude

• Caster

• Chains

• Eschalon: Book I

• Europe Universalis III Complete

• Hearts of Iron III

• Killing Floor

• Madballs in Babo: Invasion

• Sam and Max Complete Season Two

• Sam and Max Season Three: The Devil's Playhouse - Episode 2

• Simplz Zoo

• Windosill

As with the initial batch of titles available on Steam for Mac, today's additions all utilize Steam Play--meaning that one gets both PC and Mac versions with a single purchase.