As movies become more heavily franchised, it’s inevitable that more sequels, spinoffs, and homages will require more knowledge of other movies — not just for viewers’ enjoyment, but for their comprehension. Look at the biggest movie franchise in the world today: nothing about Avengers: Infinity War, from the seriousness of its stakes to the tension-breaking comic relief, makes a lick of sense to people who haven’t seen at least three or four other Marvel movies first. (If not 10 or 15.) Hardcore fans can find this interconnectivity extremely satisfying. People who just like to watch movies might find that it requires a lot of effort just to keep up with the ways these series fold back in on themselves, using fan service and multi-film plot arcs to keep audiences coming back to theaters.

The new horror sequel Happy Death Day 2U is a much smaller project than the MCU, but it doesn’t buck the franchise trend. The sequel to Blumhouse’s 2017 time-loop thriller Happy Death Day (basically a slasher Groundhog Day) does pause during its first half-hour to recap the original film for any uninitiated viewers, but that’s not its first priority. Instead, writer-director Christopher Landon immediately winks at the conventions of time-loop movies through an opening sequence that follows Ryan (Phi Vu), a side character from the first film, waking up in his car and walking to his college campus.

Before it’s officially clear that Ryan is about to enter his own time loop, Landon stages the scene to maximize all those not-so-little details audiences for these movies are supposed to remember during a character’s subsequent go-rounds; Landon gets laughs just by throwing a few obvious obstacles into Ryan’s path — a growling dog here, a guy popping out of the bushes there.

More accurately, he gets laughs from audience members who know and love Happy Death Day. In that movie, insensitive co-ed Theresa “Tree” Gelbman (Jessica Rothe) lives out her ill-fated birthday over and over, getting repeatedly murdered until she can catch her own killer and break out of the deadening cycle (and also learn to be a better person, Groundhog Day-style). Tree remains the focus of 2U; Ryan lives with Carter (Israel Broussard), the boy who Tree grew to love over the course of the first film, and Ryan’s own time-loop misadventure is something of a fake-out. During his second run-through of a day where he, too, gets murdered before starting over, he meets up with Tree and Carter. They’re quick to believe his unbelievable predicament, having just beaten it themselves. But a hasty attempt to solve his problem knocks Tree back into her birthday loop, with variations that shouldn’t be spoiled.

This means that while Happy Death Day was a horror movie about a college student stuck in a time loop, the sequel is really about a college student stuck in Happy Death Day. An obvious reference point is the self-referencing Back to the Future Part II, especially obvious because the characters directly discuss how much their story resembles that movie. For punctuation, the musical score even imitates Alan Silvestri’s trademark intrigue-twinkles from that Robert Zemeckis series. Tree, for her part, has not seen Back to the Future Part II, much to the chagrin of her nerdy friends, and she’s “so over this shit,” as she puts it when she wakes up in the same dorm-room bed for the umpteenth time. A masked killer is still after her, her new boyfriend has no memory of their first few days together, and she still gets weaker with every re-spawn, even when she takes matters into her own hands in a ghoulishly silly montage. Tree has learned to be a better person, but she isn’t entirely done growing up.

A sequel that revisits the events of its predecessor so directly and so frequently sounds like a frantic exercise in self-indulgence, which was how Back to the Future Part II was received in some corners back in 1989. Thirty years later, its reputation is much improved, and it feels like praise to point out how Happy Day Day 2U resembles it. The first Happy Death Day wasn’t especially scary, but it was clever, well-paced, and often funny. Seemingly emboldened by its success, Landon goes further afield from his original genre, even as he intentionally retreads old ground. Somehow, a slasher sequel, that lowly art form, becomes equal parts science fiction, romantic dramedy, horror movie, and zany campus comedy.

Though Landon is responsible for the movie’s ambition, he isn’t solely responsible for its success. His execution sometimes lags slightly behind his invention, as he creates scenes that could use a more delicate hand with dialogue — or better yet, with silence. A major reason the movie survives these moments, and its many hairpin turns into different genres, is Jessica Rothe. She can imbue an irritated glower with determination, pain, and comic effect all at once. Though she was funny as a mean sorority girl (and is still funny as a vexed slasher heroine), she deepens that performance with some unexpectedly emotional scenes. She grapples with mortality figuratively and literally, and she’s good at both.

Happy Death Day 2U owns its status as a sequel; based on a mid-credits scene, Landon may even have aspirations toward making this an actual franchise saga. Yet its self-referential, looped-back quality is both thematically appropriate and skillfully achieved. Another recent theatrical release, Todd Strauss-Schulson’s rom-com spoof Isn’t It Romantic, is almost as referential (to romantic comedies in general, rather than a predecessor’s narrative in particular), and not nearly as funny — or for that matter, as emotionally moving, in a sneaky sort of way. Happy Death Day 2U pulls off a trick that isn’t especially easy for original movies, let alone direct sequels: it makes all the laborious world-building and storytelling effort feel like fun.