Almost all the movement and inventory elements from Penumbra: Overture are present in this demo, which did a good job of presenting the HPL engine 3d interactive capabilities.
It has a nice atmosphere, no wonder people liked it and it went to become the series we all know and love.
It's pretty short, and has some interesting puzzles, but the roach enemy looks like a flying turd, and has little to no presence in the duration of the demo, leaving more focus to the puzzles and map traversal.
if you're a fan of Penumbra, it's worth playing to see where and how it all started.