Demos for the Linux and Mac editions of Penumbra: Overture and Penumbra: Black Plague are now available, offering the chance to check out the first-two installments in this horror series whether your PC is penguin-powered or just likes to think different. The Linux Penumbra: Overture demo is on AtomicGamer, FileFront, and Gamer's Hell. The Linux Penumbra: Black Plague demo is on AtomicGamer, FileFront, and Gamer's Hell. The Mac Penumbra: Overture demo is on AtomicGamer, FileFront, and Gamer's Hell. The Mac Penumbra: Black Plague demo is on AtomicGamer, FileFront, and Gamer's Hell.