When Final Fantasy VII hit the PlayStation in 1997, the role-playing adventure genre was changed for ever. Abandoning the stereotypical castles, creatures and grizzled beardy wizards of high fantasy, the game took place in a quasi-futuristic world the likes of which had never been seen in this style of game before. The revolutionary 3D modelled characters, the sci-fi stylings and detailed, often cinematic visuals, led critics and fans to declare it one of the greatest video games of all time.

This April, the Final Fantasy VII Remake promises to redefine the genre again, and developer Square Enix has been keen to point out that this is no shot-for-shot remake. Much will be familiar – the opening cinematic, with Cloud Strife, the game’s iconic, big-haired, big-sworded mercenary hero, arriving at the train station – has been lovingly updated, and the game’s first chapter, of which a demo has been made available this week, takes players on a beautifully re-created version of the original’s Mako reactor bombing mission.

Facebook Twitter Pinterest The retro-futuristic architecture of the Shinra building typifies the look of Final Fantasy 7. Photograph: Square Enix

But Final Fantasy VII Remake expands greatly on that world, and will be released in multiple episodes, each providing a unique experience. In the opening release arriving in April, the whole adventure will be set in the slums of Midgar, a sprawling metropolis that is home to the mighty Shinra corporation, which was only seen for a couple of hours in the original. According to the development team, this expansion will “fill in the blanks” from the original, adding depth and detail that wasn’t possible 23 years ago.

“The philosophy behind the remake wasn’t to do something completely new,” explains the remake’s co-director, Naoki Hamaguchi, who has worked on the Final Fantasy series since 2003. “The original game was grounded in the technology of the day. And because of that, there was a lot of storytelling that the player had to fill in with their imagination. In the original, for example, when you travelled between areas, the screen would fade to black; players didn’t see the journey.

“The story would have moved on and what actually happened in the meantime would be left to your imagination. We approached this by thinking, what is actually supposed to be happening here? What are the gaps it doesn’t show you, and how do we fill those in to make what was being implied actually shown? [In the original] there’d be hundreds of things happening in that one night. It feels very weird. We had to find a more realistic way of arranging that story.”

While staying faithful to the original narrative and locations, Final Fantasy VII Remake will add intricate environmental detail. Midgar now feels like a living, breathing city with fascinating new elements to discover. Take the posters on the train platform in that first mission: “We thought, who comes to this platform? What kind of information would they want? Who’d want to put up posters here? I really hope players see how deeply we’ve gone into the world,” says Hamaguchi. Elsewhere, the game’s second chapter introduces us to deadly villain Sephiroth, and plants the seeds of the history between him and Cloud, which the game will contextualise.

Some additions are more nuanced. In the first chapter of the game, as in the original, your team are on an eco-terrorist bombing mission to take down Mako Reactor 1, which is being used by the nefarious Shinra Electric Power Company to exploit the planet’s essential natural Lifestream and threatening life itself in the process.

“In the original, the character performances had to be very over-the-top,” explains Hamaguchi. Now, we get a subtle picture of what your team are thinking, breaking down the motivations of returning fan-favourite character Barret. “You don’t just see his gung-ho attitude. After they blow up the reactor, he has doubts and internal conflict. He obviously believes in his cause, but he’s wondering if he did the right thing.”

Together with the extra storytelling time, refined voice acting performances will add to the authenticity of the world. Battles, too, are faithful to the original’s gameplay – but more dynamic. And importantly, more fun, employing a hybrid of the original’s complex Active Time Battle system with real-time combat. It’s a clever combination that is both fast-paced and strategic.

In line with the classic ATB setup, you must wait for your character’s gauge to build up in order to use magic and to heal, but can use real-time battling to thrash your other weapons at enemies in the meantime. You must switch wisely between those in your party to use their move specialities against appropriate boss weak-spots, too. Cloud’s huge sword is as satisfying as weapons come for close-quarters melee attacks, while Barret’s machine gun (handily also part of his arm) is best used for long-range attacks; Tifa employs martial arts skills, and Aerith uses support-style magic to aid her allies. It’s a lot to think about in the heat of a boss fight, but the complexities make battling rewarding.

Facebook Twitter Pinterest Final Fantasy 7 Remake overhauls the original game’s Active Time Battle system with real-time elements. Photograph: Square Enix

“We really did look at what made the original Final Fantasy VII what it was: all the characters, the story, the mini games.” says Hamaguchi. “We’ve definitely got mini games …” Considering the remake is all about nuance and naturalism, it is surprising to hear that mini games will return: it’s difficult to imagine the retro, old-school hangover of this convention being part of the industrial, gritty, highly-defined Midgar world. And yet, some of the most abiding memories of the original game are tapping buttons in a specific order to do squats in the gym at the Wall Market, slicing left and right on your motorcycle in the G Bike game, or tapping furiously to arm-wrestle a sumo warrior in the Wonder Square. And who can resist a Chocobo race?

“They’re all in there,” confirms Hamaguchi. “We didn’t just reproduce the ones from the original game; there really are a lot of different mini games there.”

Now that the first episode of Final Fantasy VII Remake is almost here, the team is working on its sequel, which will take us further into the world beyond Midgar. There’s no word yet on how many more instalments there will be beyond that, but the developers have been open about the saga continuing for not years, but decades, with producer Yoshinori Kitase, another Final Fantasy veteran, announcing that he plans to work on it for the rest of his career. And there is certainly rich enough material to carry it on for as long. It is clear, once again, that there is nothing at all final about this fantasy.

• Final Fantasy VII Remake is released on PS4 on 10 April.