The final play in the often brilliant Nicholas Hytner era at the National Theatre is a good 'un. During Hytner's dozen years there was a period during which it might have been said there was a weakness to the National's output - the category of new writing, and that was despite The History Boys and War Horse, both huge new-writing hits.

But that blemish was burnished away years ago and Sam Holcroft's first full-scale play to be incorporated into the National's season is typical of the venue's inventive and ambitious new work. Incredible then that the setting of Holcroft's family tragicomedy is just about as hackneyed and clichéd as the writer could have imagined. It is Christmas day and two underachieving brothers in early middle age have returned to their parents' home to celebrate - as one of them sardonically puts it - the birth of a Jewish radical in the Middle East with pork cocktail sausages.

The married one, Adam (Stephen Mangan) is with his depressed wife and the unmarried one Matthew (Miles Jupp) has a deeply gauche girlfriend in tow; she wears shocking pink and blurts out dirty jokes in the presence of the boys' well-to-do parents, or did the last time they met.

It's all terribly Ayckbourn, which for most people is a good thing. But on to this familiar territory Holcroft has constructed an extra dimension - a game show. Each character in the play has to accumulate points by completing tasks displayed on a score board. Chloe Lamford's design emphasises the concept by setting the action on a giant game board, as if everything on stage had been placed there by unseen hands.

A klaxon sounds; the play freezes. A new rule appears and we're off again. For instance, Sheena, Adam's possibly alcoholic wife, can only contradict someone if she has a drink. Or Matthew can only lie if he eats, which, when he has to deny that he is in love with Sheena, results in him stuffing his mouth with the only food available - a bunch of thyme that he has just picked from the garden.

Like many a game, it all seems fun but rather pointless. But what emerges is the realisation that each of our behavioural ticks are driven by psychology. So once you know the rule that drives a particular response to a situation you know what that person is trying to hide. Put another way, it's like playing poker and knowing what, as seasoned gamblers call it, your opponent's "tell" is. When they're bluffing they might scratch their nose, for example.

The National has thrown some stellar talent at the play including Mangan, Jupp, Deborah Findlay as the shrill matriarch (has to clean to cope with stress) and director Marianne Elliott who was co-director of one of the Hytner's early new writing successes, War Horse. This painful and often hilarious comedy could go on to be every bit as successful.