Co-op play rules (page 20)
To play Sol as a cooperative game: use all the rules for the playing the Solo Variant, with the addition that the final score for everyone as a group is the score of whoever has the least momentum! When constructing the instability deck, use the solar flares + one suit per player + one extra.
In addition to using one of the scenarios, you can play a straight cooperative game: pick 3 instability effects to use in the game, and assign suit tokens to them as evenly as possible (so some effects may have more than one token assigned to them). You all collectively win if the lowest scoring player has at least 13 momentum. To increase the level of difficulty, raise this number in increments of 3. Now Sean’s favorite way to play!