Primer: parents' guide

Brief and realistic: one man smothers another, a character is knocked out, and there is a short scuffle. Characters talk about a man threatening people with a shotgun at a party, and the gun is glimpsed. Time travel makes the men's ears bleed.

Infrequent. Expect "hell," "prick" and "jacking around," plus a homophobic slur. Movieguide counted four mild obscenities and two profanities, and the MPA cited only brief language. No f-words were reported.

Nothing sexual. There are no romantic scenes or nudity; the story stays focused on the two men and their invention.

Light overall. Adults drink at a party and some smoking is shown. The men take motion-sickness pills before using the machine, and one character secretly drugs another's drink to knock him out.

Little that is scary. There is a tense subplot about an armed man at a party and a creeping paranoia as the men lose track of their doubles, but the confusing plot is more likely to frustrate than frighten.