It is made abundantly clear throughout the demo that
Linger in Shadows is not a game, though there are a few interactive elements for anyone who wants to earn a few Trophies. During the presentation, you can use the SIXAXIS controller to control the camera or rewind and fast-forward through different parts of the demo. At times, you can also tinker with objects, like playing with the lighting, though these occurrences aren't common. There are no obvious "missions" or anything pointing you around the demo (though there are a few audio clues to guide you); instead, you are free to explore and see what you can see. If there is an objective to your search, other than get through the entire demo, it is to find various "greets" or shout-outs to other artists in the Demoscene - though these will likely matter more to people familiar with the scene.
At the most, Linger in Shadows is a unique experience, though only if you're either into the Demoscene or have an interest in games as something other than something you play to kill a few hours. If you find yourself in either camp, Linger in Shadows is available in the PSN store for $2.99.