Science-fiction cinema doesn’t always require terrible digital special effects and huge-name actors. Coherence is a charming littleparlor game of a movie, following a group of friends at a dinner party who stumble into a confusing state of quantum dissonance as a reality-warping comet flies by overhead. Some of the acting is TV-level (Nicholas Brendon—Xander from Buffy the Vampire Slayer—is the biggest name in the cast), but as the movie opens up into its own weirdness, you forget about the budget and become engrossed in the concept. You’ll want to watch Coherence twice. (Grand Illusion, 1403 NE 50th St, grandillusioncinema.org, 7 and 9 pm, $8, July 18–21)