How did Marji’s dad bring light to the darkness at the party?

They basically drink wine. The Satrapis hold a party to celebrate Marjane’s aunt and the birth of her child. The parties are necessary because “without them it wouldn’t be psychologically bearable....” During the party, the power goes out and there is no light. The party continues, however. The guests even have wine because Marjane’s uncle is a self-taught vintner and has set up a secret wine making lab in his basement.