Frictional Games has released Penumbra: Requiem
( for Mac and Linux systems. The puzzle
expansion for Penumbra: Black Plague costs US$9.99. Also, Frictional
Games is offering all three Penumbra games as a collection for $35.

Penumbra: Requiem has previously been released for Windows by
publisher Paradox Interactive. Here’s how the expansion pack is
described: “The game contains numerous physics based puzzles, spread
out over 9 levels with unique settings. The expansion pushes the
graphics capabilities of the game as far as it can – while creating
the most detailed and dreading environments yet in a Penumbra game.
The expansion gives extra details to the characters from previous
Penumbra games, taking peeks into their final moments of insanity.”

The Penumbra series is a first person survival horror series of
games, emphasizing survival and problem solving. It’s played from a
first person perspective and powered by a 3D engine.