You can get an idea of the gameplay from one of their recent trailers below:
Here's what they said:
We are working harder than ever on making SEVEN: The Days Long Gone the best game available on Steam. In the past couple of months, we've got many questions about potential releases on different platforms. That's why we decided to ask you that theoretical question, which may lead to final decisions if the game happens to be a success:
Which platform would you like to see being supported from our side next? Consoles, PC dedicated online platforms, mobile or maybe even Casio calculators ;)
We are curious what you think our next step should be, and we're waiting for your comments below.
It's not often you see a developer specifically ask for platform suggestions, so why not head to the Steam post and request a Linux version if you would purchase it.
Personally, I think it looks like exactly the type of game I would play, so I would like to see it on Linux.
Thanks for the tip micha!