Four hotshot mathematicians (oh, they exist!) find themselves in a spot of bother when, having solved a riddle posted to them by the illusively monikered ‘Fermat’, they are duly invited to an ego-fanning ideas symposium in the countryside. On arrival, they are locked inside a sleek boudoir where they are forced to answer fiendish maths teasers on pain of death by crushing… or at least that’s what we’re led to believe. Sadly, Spanish writing-directing duo Luis Piedrahita and Rodriga Sopeña are more interested in building on a tortuous, illogical set-up than developing a way to make the maths problems (and the protagonists’ lives) worth giving a fig about. It’s more than competently directed and performed, but you’ll be pulling your hair out as time ticks down, deadlines are passed, walls slowly cave in and you’re still being force-fed huge blocks of flabby, overly intricate backstory. The maths element of the film, which on the surface is its USP, feels like dressing on a taut but tawdry genre thriller.