Will it be playable alone offline?

[*Yuki*]

Or its one of these games, that built around coop and streams and wont play well alone?

[Dieharders]

Absolutley you can play single player. It's 1-4 players, so any # of people can play and it doesn't depend on having others (like an online game would).

And if you are already playing, others can drop in and drop out any time without affecting gameplay.