The Untouchables, which arrived on 8-bit and 16-bit almost two years after Brian De Palma's 1987 movie had been a sizeable critical and commercial hit, felt marvellous at the time: an expansive, polished Prohibition-era shoot-em-up that offered up six relatively distinct mini-games. Thankfully, none of them involved completing a sliding block puzzle of Sean Connery's scowling face as Irish beat cop Malone, although many included the illicit thrill of a bootleg liquor gauge, even if your dogged G-Man was mostly destroying the booze rather than imbibing it. My experience on the Spectrum should have been the most lo-fi of all the home computer versions, but it somehow seemed like the classiest - enviably crisp sprites rendered in a consistent palette of black and cool blue, accompanied by a series of digitised mugshots that kinda, sorta looked like at least some of the actors.

Intentionally or not, The Untouchables was also a system-seller, as the downside of having six completely different levels was having to load almost every single one of them separately. Ownership or access to a disk-drive-enabled Spectrum +3 was absolutely essential for maximum enjoyment. On old-fashioned cassette, the tussle for Chicago supremacy between Eliot Ness and Al Capone became a downtime-punctuated crawl. To exacerbate matters, the first level was actually the worst - a platform scramble round an anonymous warehouse, with you as Kevin Costner's dourly single-minded Ness, tasked with gathering evidence against the notorious crime boss through the time-honoured process of wasting gangsters, hopping between precariously-stacked pallets and picking up violin cases to access a Thompson sub-machine gun.

Even Ocean must have suspected that floaty platforming didn't showcase their game at its best, as they widely released the second level as a demo instead. This turned out to be a masterstroke, because that instalment - based on a bootlegger shoot-out on a bridge at the Canadian border - is the best of the lot. In the spirit of the arcade game Cabal, it's a thrilling shooting gallery where your character is also visible on-screen, rolling across the ground while firing off rifle rounds and destroying hooch barrels. A separate binocular scope nominally shows where you're aiming, but it's pretty easy to gauge from the trail of dustclod ricochets and trenchcoat-wrapped bodies you leave in your trigger-happy wake.

The third level, where you heft a shotgun in a tense alleyway shootout and swap between your four Untouchables to keep the mission-vital ones alive, is almost as good. But it's level four - where the action switches from side-on to top-down - that is especially memorable, as it recreates the most iconic scene in the movie, a haphazard shootout at a railway station that takes place while a baby's pram bumps through the crossfire. It was De Palma's celebrated, agonisingly drawn-out tribute to the Odessa Steps massacre in the silent movie classic Battleship Potemkin.

Just as BDP atomised and expanded what must have been a pretty sparse page of script - there's no dialogue, apart from a mimed scream of "my baby!" from the panicking mother - so the game extends it even further, charging you with managing the health of both Ness and the baby. Admittedly, it's another shooting gallery, albeit one that gives you the morally questionable option to use the pram as a temporary shield, safe in the knowledge that you can subsequently hustle it toward a restorative first-aid kit at the next landing. But 25 years on, another thought occurs: did The Untouchables accidentally invent the dreaded escort mission?

In the movie, the sharp suits for gangsters and G-Men alike were designed by Giorgio Armani. The score was just as lavish and lovingly tailored: a sumptuous, thrilling, Oscar-nominated suite by Ennio Morricone, It's unclear whether Ocean ever had the option to try and recreate the work of the Italian master, although 8-bit sound chips would certainly have struggled to recreate the querulous mouth organ and slightly detuned piano that characterise his soundtrack.

Instead, they opted for a very different but ultimately inspired route. Jonathan Dunn, Ocean's astonishingly talented in-house maestro, adapted the chirpy rags of Scott Joplin, imbuing the game with a bouncy, cheery energy that - while slightly at odds with the demands of mowing down dozens of wise guys - gives it an undeniable vim and vigour. It may have triggered a little cognitive dissonance in historians and cinephiles - ragtime was on its way out by the time Prohibition kicked in, and the syncopated style was also indelibly associated with The Sting, another sharply-tailored period piece - but it undeniably helped synthesise a cohesive identity for a potshot-pourri of a game. Deployed alongside the uniform colour scheme, it helped bind the disparate levels together, and make The Untouchables one of the most aesthetically successful video game movie adaptations of all time.