Filling the gap created by the absence of combat, the puzzles provide the primary source of entertainment and challenge in Penumbra: Black Plague. Most of the puzzles are physics-based challenges involving using objects available to manipulate the physical environment, and they’re all 100 percent logical. Some of the puzzles even have more than one solution. Thus the puzzles aren’t the frustrating sort many adventure gamers are used to, where you have to do annoying pixel-hunting or combine everything in your inventory with everything in the environment to get something to happen that makes no sense. Instead, for example, you use the metal bar to pry open the locked door, or drag some boxes into the correct position to allow you to jump across some obstacle. Some puzzles do require that you interpret some written instructions in dealing with your predicament, but nothing is ever too complicated, and you’ll find yourself stuck only for a short time.

To manipulate objects in your puzzle solving, you engage in realistic interactive mouse movement. Opening a desk drawer or a door involves clicking on the handle and then pulling back so that it will open; throwing an item involves moving the mouse rapidly forward; flipping a lever involves clicking on it and pulling down; and turning on a valve involves rotating the mouse realistically in a circular motion. It’s sometimes, however, a bit tricky to move stuff around in just the way you want, especially when you have to get an ungainly item into a particular place in a particular rotated state. A related great feature is that you can smoothly and convincingly interact with the computers strewn throughout the complex: whether you’re reading a text file, opening locked doors, listening to an audio file, examining pictures of places you have yet to go or videoconferencing. Overall, the challenges are more mental than physical, for you have to think carefully about the physics of motion.

As with its predecessor, what makes these environmental puzzles so enjoyable is the superb physics implementation. The real-world authenticity is extremely high, whether you’re building something, using one object to smash through another or simply sliding an item around. This time around, Frictional Games added the ability to rotate the objects you hold, adding additional exciting wrinkles to your environmental interaction. While not absolutely necessary, this skill allows you to have fuller control over the environment. You can stack objects, build bridges or platforms and really have fun playing with everything you see. Nothing is tied down, and many objects can be broken, allowing a ton of interactivity and opportunity for creative innovation. If every moment involved time pressure, problems might ensue in this regard, but fortunately, this isn’t the case.

The atmosphere in Penumbra: Black Plague is eerie and at times terrifying. Being alone in the dark with nothing to protect you leaves you permanently insecure. If you think you’re safe for a moment from your enemies because there’s a locked door between you and them, think again — they can break through such a barrier and come and find you.

What with a plague or evil force affecting everyone, you never know what to expect or from where your next challenge will emerge. Because you’re infected, your mind is partially controlled by the infection, and so you can’t necessarily determine whether you’re hallucinating or trust what you see and hear. You become disoriented very easily. The occasions where you have a sense of real urgency heighten the suspense still further. Ultimately, you probably won’t be able to get a peaceful sleep after an extended play session.