Bought Penumbra collection a few years back from the site- steam code?

[Bouc]

Thanks guys. I actually added it to Steam as a non-Steam app right now. However, when I try to run it, it asks me for a serial. I don't remember having to enter one when I first played this—I just downloaded the game off the site (I think once you bought it, you got your own special URL to download it). There's only a Penumbra License rtf in the main folder, but it's the user license agreement thing. I'm so confused!