This four-person sci-fi play depicts an apocalyptic world with a crushingly heavy hand. Explainer lines fill in gaps left by the sparse setting, leaving no room for life, light or even imagination. The trees are gone. Humans ruined the sun. The world is doomed. The characters, played by mostly Fringe newcomers and directed by the playwright Logan Toftness, don’t know how — or if — the world should go on. But the show must, and the effort to carry it to a cliffhanger ending earns admiration, if not a few groans. (1 p.m. Sun., 8:30 p.m. Tue., 1 p.m. Sat., 5:30 p.m. Sun., Ritz Theater Proscenium, 345 13th Av. NE., Mpls.)