30 years on, Metal Slug's arcade action and stylish visuals owe Studio Ghibli a debt: "We were very much inspired by Hayao Miyazaki's book, Daydream Note"

Although now easily available thanks to several mainstream re-releases, Metal Slug has long been a focal point for the hardcore. Developed at a time when 3D was usurping sprites both in arcades and at home, it showcased what was still possible with 2D. It was also developed for SNK's Neo Geo hardware, which epitomised rich and cool. Even when ported elsewhere, such as to Sega's Saturn, it required an additional RAM cartridge to function, reinforcing the fact that it was special. Whether in arcades or as a console port, Metal Slug is something that today remains aesthetically and functionally beautiful.

Yet for a long time we didn't really know who made it. While Metal Slug has become synonymous with SNK, it was actually developed by the mysterious Nazca Corporation, an offshoot of Irem that was later absorbed into SNK, and a company that many know little about. It's also hard to even get interviews via SNK Playmore, as many of the original developers no longer work there.Further complicating things is that the original series is credited only to a series of mysterious pseudonyms: Kawai, MeeHer, Akio, Susumu, Cannon/Max-D, Tomo, Kuichin, Andy, Seeker and Hamachan. Also, with the exception of a transcript in the Metal Slug Anthology release and a surreal Q&A with MeeHer on Metal Slug Database (mslugdb.com), there don't appear to be any interviews with the team – at least not in English.

Pedal to the metal

A breakthrough was made when previously unpublished excerpts from an interview with Irem's Kazuma Kujo were leaked on the old Insert Credit forums. Detailing his background, Kujo revealed that he wrote the original concept for In The Hunt (aka Kaitei Daisensou) at Irem and oversaw its development, later helping to form Nazca and taking charge of the Metal Slug project. But to fully understand Metal Slug's creation, you need to go way back, since in many ways it's an evolution of scrolling shmups such as Irem's R-Type, rather than traditional run-and-guns like Contra.

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After joining Irem, Kujo's first job was helping playtest R-Type II, though he wasn't involved in design. His first creative role was on In The Hunt, which was released in arcades in 1993. It was an extremely detailed 2D shmup featuring submarines, a simultaneous two-player option, and the ability to manually move the play area forwards.

All of this, according to Kujo, owes something to the vast range of other shooters available, including Irem's own R-Type: "The plan to make a 'shooting game' had already been decided, but also, at the same time, I had decided to make the game for two people who could play simultaneously. However, I did not like that in shooting games there was forced scrolling, so the screen would just keep on moving even if one of the players was out of the game. Also, most shooting games were set in outer space, and I wanted to make something different."

It certainly was different, with a tremendous amount of personality in the submarines you controlled, enhanced by detailed animation for everything on screen. The inspiration for the submarines may come as a surprise, though. When asked, Kujo laughs: "Well, for a long time I could not come up with any good ideas, and for about a month I would sneak out of the offi ce every day to think in the park. One day I was dozing on a park bench near a fountain, and, hearing the sounds of water, I had an inspiration: 'Water… like a submarine!' And so I decided to make the game using submarines."

From here, things get complicated, since the following year Irem released GeoStorm (aka Gunforce II) in arcades.This played and looked like a prototype Metal Slug, with a visual style similar to the preceding In The Hunt but containing no developer credits. Several other Irem games, such as Undercover Cops, also had a similar style to what would later be seen in Metal Slug. We ask Kujo if he was involved with any of these, specifically GeoStorm. "I was not involved in those," he replies. "My colleagues made them."

Rattling off the names, we ask if he remembers people such as Akio, Susumu, MeeHer and Hamachan, plus who they were and why no one was named. He explains: "Yes, I remember them. At that time, Japanese game companies were very cloistered, like a closed society, and to announce their real names was prohibited. Therefore, we used our nicknames instead." Unfortunately, he refuses to give up their identities.

Equally as clandestine is Nazca itself, which was allegedly formed from Irem as a result of the company's inactivity. Kujo confirms this: "It is true. Nazca was founded with around 15 employees from Irem. [At that time] I served at Nazca." Of course, he has officially only ever been employed by Irem, implying that his role on Metal Slug was a case of moonlighting.

If In The Hunt was an evolution of galactic shmups like R-Type, Metal Slug started as a direct successor, albeit with tanks replacing submarines. It isn't until towards the end of the interview, when we ask Kujo about what challenged the team most, that this bombshell is dropped: "The most difficult point was significantly changing the configuration of the player. Originally, the combat vehicle was the only character you controlled. However, when we did location tests, we did not get a good response from customers playing. So, we changed the game so that the soldiers were the central characters you controlled."

When asked about other changes, Kujo's memory is blurred: "I think some parts of the stages were remade, but I cannot remember it clearly." However, the team transcript in the Metal Slug Anthology reveals that after changing the characters, other things had to be altered: "In order to create and release one game, tons of ideas or designs are born and destroyed. In the first title, there was a stage [on which] we had to redraw almost half of the background graphic because it ended up not matching our direction as development progressed."

It's astonishing to think such a radical change had to be made after the game was already complete and being location tested. Unsurprisingly, the personality of the eponymous Metal Slug tank was well established. The Anthology transcript reveals that the team had found inspiration in several sources: "Well… We want to say, 'It's an original idea and we didn't get any inspiration from anything!', but actually we came up with the design from various manga, animation, movies and other places."

We show this to Kujo and ask for elaboration. His candid response should please Studio Ghibli fans: "Oh, there was definitely other influences. We were very much inspired by Hayao Miyazaki's book, Daydream Note." Curious readers should track this down, since it collects various manga by Miyazaki, first published in 1992 in which form it likely influenced In The Hunt and Metal Slug, and again in 1997 with additions.

Viewing the exquisite watercolours in Daydream Note, the inspiration is clear, but at the same time we can't help but wonder if Masamune Shirow's design for Bonaparte, the tank in Dominion: Tank Police, also played a role. Although freely admitting the influence of Hayao Miyazaki, the response from Kujo regarding Masamune Shirow is surprising: "It was not taken from Dominion: Tank Police. I cannot answer about this any more."

To appreciate what Metal Slug represents, you also need to understand the context of the mid-Nineties, when the PlayStation was the dominant home format and SNK's ageing MVS hardware was starting to look obsolete alongside its competitors. As Kujo explains, support for an old arcade format was simply because that's what they knew: "We were making games for game centres – or arcades, as you call them – when we were in Irem. So that is why we made games for Neo Geo at Nazca, since that was the hardware of game centres."

Using SNK's hardware resulted in Metal Slug having a beautiful and extremely ambitious 2D form, despite being released at a time when everyone was obsessed with 3D. Long-time fans who believe that this would have been an artistic choice may be disappointed to discover this wasn't the director's intention. Kujo explains that, after In The Hunt, his interests were no longer in sprites: "I did not specifically mean to make 2D games. It was just because the game machine, Neo Geo, that we were working on at that time was 2D hardware. After I left Nazca I made R-Type Delta and other 3D games."

Of course, nothing can detract from the genuine artistry of Metal Slug's visuals, and Kujo confirms the amount of work that was needed, though he reveals something surprising: "Our artists took quite a long time and worked very hard to make the graphic designs. However, we made the 2D animations for those graphics at a menacing speed. We needed a lot of energy to make them, but we made those graphics much quicker than you imagine."

The Anthology transcript backs this up, explaining how delegation of the workload allowed for faster completion: "Basic art and animation moves for the enemy characters were planned and designed mostly by the chief designer exclusively. That is the big reason for consistency throughout the series. After the basics were done, they were sent to other staff to put actual movement and animation patterns."

Asking about Kujo's favourite part of Metal Slug reveals an interesting design decision: "I like the fact that the central characters, the soldiers, can only shoot directly upward and not diagonally. We spent a lot of thought on this, and I believe this is the way to do an action shooter!"

The inability to fire diagonally when on foot, compared to run-and-guns like Contra, is what mechanically ties Metal Slug to traditional shmups like In The Hunt, since the restricted vertical and horizontal shooting conveys a unique feeling. Although the heavy machine gun can technically fire at an angle, this is haphazard and only the result of its animation swing – for genuine oblique firing, you need to enter the Metal Slug tank, which acts as a power-up.

As for the rest of the team, the Anthology transcript offers insight: "We really like the shotgun because the shooting range is so short that you have to take a chance to get closer to enemies to take advantage of the destructive power. We also like the Morden soldiers because their programming is very complicated, but they are beaten so easily."

Before parting, we ask Kujo if he's played any of the sequels and what he thinks of them, since he left the series after the fi rst game and the rest of the original team only remained intact until the third instalment. "They sound good," he admits, "especially the part where you can ride camels, but I don't know because I haven't played the sequels much."

Special thanks to Kazuaki Yazawa and Yuko Ogawara for their translating help, and Samuel Melzner for his assistance. Check out our best Neo Geo games ranking for more retro classics to play!