Half-Mean Girls, half-Strangers on a Train, all loving homage to as many teen comedies as you can think of, with a pair of passable lead performances (Maya Hawke did not do much, but Camilla Mendes amped up her soap tendencies from Riverdale to delightful effect) and a script that (to my rapidly aging ears, at least) nailed the transformation both of dialect and dynamic over the past ten years: the villain is not a turbo-jock but "fake-woke", and the quips were delivered with a solid level of panache.
The twist (which Haley and I guessed, but I don't think it's a film that was meant to leave you agog) was fun: there is no better trope in film than the "here's a replay of seven different scenes with a different implication and tempo now that you know The Twist", after all.
The final act was — a bit messy, a bit rushed. The script really leans into the deep sociopathy of the two leads, and then abruptly leans out of it in a way that defies logic even more than the preceeding convolutions. (I also thought the more earnest ending — the leads ending up as friends, sans their romantic entanglements — was betrayed by the mid-credits romantic sparks reigniting in both couples, but alas!)
(Also, Sophie Turner in a bit role yelling about coke — comedic gold! Was not expecting that.)