Nathan likes maths. He likes prime numbers, prawn dumplings, patterns and his dad, but he doesn't like mess or unfamiliarity, and he's not too keen on his mum (a brilliant Sally Hawkins) who's "not clever enough" for him. Nathan (Hugo's Asa Butterfield) is mildly autistic, and sees the world differently way to other people.
He's really good at maths, so his primary school arranges a tutor, Martin (Rafe Spall) - who took part in the International Mathematics Olympiad, and who thinks Nathan could do so, too.
X + Y is based on director Morgan Matthews' documentary, Beautiful Young Minds. It provides a glimpse into a highly competitive world where Nathan learns about maths and life outside his comfort zone; but more importantly, like the novel The Curious Incident of the Dog in the Night-Time, it explores how people with autism see the world, and how their condition affects those trying to get close to them.
All the performances are great, particularly Hawkins as a heartbroken mother trying to do the best for her son. The plot stays just this side of reality to avoid Hollywood-esque clichés, and while there's romance, those involved are flawed and human enough to avoid mawkishness.
A brilliant, educational, bittersweet, but ultimately uplifting film.