We are launching a game Hall of Fame and Discworld Noir qualifies, for being the best scripted game we have played

So what exactly passes for a classic in this relatively youthful medium of gaming? There is a desperate need to establish a canon of classic games against which their mediocre rivals can be judged and damned.

This means that many games pass from review copy straight to the Hall of Fame long before the gaming public gets a chance to cast its vote. Never mind the test of time: if a game's been out for three months without too many glitches or bugs, hell, let's repackage it cheaply as an instant "classic".

So what are the criteria? Let's take Discworld Noir as an example, often hailed in the more literate mags as such, and now available very cheaply on budget. DN is the third of the spin-off games from the best-selling Terry Pratchett novels. It's a detective thriller, but much more loosely related to the novels than the previous two games.

This is a mercy if you don't happen to be a big fan of Pratchett's bottom-gag slapstick, or are indeed a tad embarrassed to be associated in any way with the hordes of Student Grants in hash-burnt knee-length jumpers who flock to touch the hem of Pratchett's safari suit at every public reading that he gives.

DN is still set in Ankh-Morpork, but it has an entirely new plot and characters, and takes its cue as much from film noir and Raymond Chandler as Discworld's comedic fantasy. Pratchett was closely involved in the development of the game - his job title is listed as "Far Too Much Interference" on the credits - but Chris Bateman should take equal plaudits for a script that displays a level of wit you simply don't associate with PC games.

It is just as well as this is a very talky game indeed. Grim Fandango, which is comparable in action gameplay, has 7,000 lines of dialogue. DN has 16,000. The pedigree of the actors is impeccable: Rob Brydon, Robert Llewellyn, Nigel Planer and Kate Robbins - veterans of Spitting Image, The Young Ones and Red Dwarf - make a versatile and skilful team. But there are only four of them, which, given the huge cast of characters they play, makes for the wrong kind of laughs as you listen to what sounds suspiciously like the same actor talking to himself in different regional accents.

Full marks, though, for Noir's music and sound world, easily its best single feature. The composer Paul Weir has supplied an extraordinary range of musical textures, from the sleazy swing of a jazz club to faux Schoenbergian tension builders. The introductory music wouldn't sound out of place at a Proms concert.

Another attribute of a classic should be its fitness to its purpose, a sense of all its elements being held in an internal balance. This is where a clear and clean interface becomes so important.

In Discworld Noir the gameplay is simplicity itself - the point-and-click system uses a torch beam to highlight the objects or places of interest in a scene. There is a simple inventory, and a notebook for clues. Best of all, about halfway through the game our hero, Lewton, becomes a werewolf. When the "dog's nose view" is switched on, swirls of coloured pungency become visible. He can investigate these for more clues, while trying to resist the competing attentions of lampposts and trouser legs.

We loved the shadowy sets, and the end-of-LP crackle of the perpetual rain that put us in mind, inevitably, of the film Seven. The only real disappointment is the pre-rendered 3D and, in a less-witty game, we would not have long tolerated all the characters jerking around their fixed backgrounds like Captain Pugwash.

That said, Discworld Noir is just about the best scripted and best scored game we have played, and - with admittedly little competition - deserves its place in the canon. The look of the game will date very quickly, but then, who thinks less of Psycho for being in black and white?

All software reviewed in Interface is available from The Times Software Shop on 01874 612888 or at www.times-eshop.co.uk

Paul Weir of Earcom (composer for Discworld Noir):

"Any exposure of game music within the national press is good news for us sound designers in demonstrating to the wider public the sheer quality of our work within this industry."

Chris Bateman of International Hobo (co-designer and script writer for Discworld Noir):

"Discworld Noir used a prototype dynamic scripting language to produce rich, context-dependent dialogue quite unlike anything previously offered in adventure games. We're very pleased that our staff are being praised for this achievement, and we would like to thank producer Gregg Barnett for giving us a chance to try this innovative new approach."