IN the fantasy universe, why shouldn’t an old-style computer game take on a form of reality by drawing players into its imaginary situation and confronting them with rules that they must obey if they are to survive?

Jake Kasdan’s film, written by Chris McKenna, adapting a book by Chris Van Allsburg, introduces four high school kids. Spencer is a weedy dweeb. Fridge is a black footballer disenchanted with school rules. Martha is socially dysfunctional. Bethany is obsessed with her smartphone. In detention for campus misdemeanours, their task is to tidy up a disused junk room, where they find a computer game from perhaps their parents’ era. Playing is more fun than destapling old educational texts destined for recycling.

For the game, the kids select their avatars. And suddenly they are in the jungle. Spencer, has become large and powerful. Scientist Fridge’s backpack holds everything an adventurer needs. Martha becomes an unarmed combat exponent. Although an archaeologist, Bethany still needs her phone.

In a jungle where the wildlife conforms to no known geographical habitat, their task is to recover the huge, green jewel that bad guys have stolen from a giant rock jaguar to which they must restore it if they are to win the game and get back to their real selves.

It’s a movie for kids of any age, filled with narrative non-sequiturs, performed with brio. As Spencer, Dwayne Johnson, earlier in his career called The Rock, shows comic skill. As Martha, Karen Gillan’s unarmed combat is impressive. Kevin Hart carries Fridge’s backpack with élan. Playing a teenaged girl, Jack Black reminds us of his comic versatility.

It’s energetic, predictable (which in this kind of movie doesn’t really matter) and totally undismayed about not carrying any message.

At all cinemas