Having started life as little more than a pet project for developer Jonathan Biddle, Stealth Inc: A Clone in The Dark has ended up rolling out on PC, consoles, and importantly for Pocket Gamer PS Vita.
It doesn't stop there, either. Biddle is currently working on an iOS version. Not bad for an experiment.
In this week's making of, we track the game's progress from hobby to full on commercial product, touching on one other sensitive subject what to do when your game's name is full of profanities.
Born in shadow
"I've always had hobby projects that I do in my spare time," Biddle explains.
"At least, ever since I picked up Game Maker. The first I did was Explodemon, which - although I never released the original 2D version of - we eventually ended up doing a proper 3D console version for PS3 and PC.
"While we were making Fluidity for Nintendo and Explodemon for PS3, I was pottering around with Game Maker in my lunch breaks, playing with a shadow system I'd found.
"I'd bent it to work well with a platform game setup, and I was planning on doing a Metroidvania-style game, where the player was a type of bounty hunter who arrived in a spacecraft on a planet's surface and infiltrated facilities using stealth.
"I had a bunch of ideas for lots of gadgets, weapons and a type of cover system, and it was all sounding quite interesting, but I cottoned on to the fact that it was getting out of hand."
It's often the case with game design, that a game's ambition can extend beyond its reach, eventually ending up a convoluted mess. The best designers all seem to have one thing in common: they know when to kill their babies.
"What I want from my hobby projects - or at least what I wanted at the time - was to try stuff out, make something small and polished and just learn from the experience," remembers Biddle.
"So I stripped it all back, took out all of the weapons and gadgets and kept it to a single screen. The goal was changed to 'get to the exit' and I removed everything that was irrelevant to that.
"I really only wanted to make something small, very quickly, so I could then move onto something else and repeat the process, but somewhere along the line I realised I had to create an in-engine level editor, which made me investigate creating a level sharing system, and it all got out of hand."
It's another common occurrence that a single idea can end up snowballing, ever increasing in scale until the project either grows, or cuts right back. At this stage, Biddle decided on the former.
"Other people around the office started to notice that it was actually quite good - I wasn't particularly enamoured with it - and we discussed doing something more with it," says Biddle.
"That's when we added art, got some of our level designers involved and released the original free version of Stealth Bastard in November 2011."
Biddle says that, because in his mind "it was only ever a hobby project", it simply "didn't feel right to charge for it".
"Subsequently, it got picked up everywhere, ending up with more than 150,000 players," he admits. "It surprised me, to say the least."
Biddle had worked on the game for around fifteen months before others got involved with what was once a very personal project.
For the free version of the game, Biddle worked with an artist, two level designers and an animator an animator who also worked on the game's music.
"I did all the code and made half the levels myself," he explains. "We picked up a Steam slot based on our success with the free version, and - instead of just putting a slightly enhanced version on there - we set about creating a fully blown sequel, Stealth Bastard Deluxe."
For the Steam sequel, the team's size was increased once more, as Biddle set about adding 80 new levels to the game, as well as new features and a graphical makeover.
"Time was tight on creating that version, though," Biddle continues. "We wanted to release by the end of November, and we could only really get going after we finished Fluidity Spin Cycle on 3DS for Nintendo, which finished in August.
"The plan was to roll a lot of the team from that game onto Stealth Bastard Deluxe and do it all in three months, which we managed in the end. So for Stealth Bastard Deluxe, there were four level designers, four artists, and I did all the code, and designed or directed it. But again, all in three months!
"We put the final version up on Steam three hours before it was going to go live, so it was right up to the wire."
It was a huge undertaking for the small team, but they managed the mammoth task successfully - which Biddle says was down to the quality of his team.
"We all work well together," he explains. "And we were still working at full speed after having just come off Fluidity 3DS.
"The game was mostly formed since we had the free version, so we just had to design a lot of levels very quickly alongside prototyping the new features we wanted. It was a lot of fun really."
And the new features were many. "We added a lot of game objects, such as the noisy floors and the sensor beams," Biddle continues.
"We also added the boss characters - the sentinels - and the sliders.
"Both Stealth Bastard and Inc by design try to create a lot of different interactions with as few objects or rules as they can.
"For example, the sensor beams, [which] are interesting because they act as triggers for anything in the level, are blocked by moving platforms and moveable blocks, but can be triggered by both enemies and the player. They can also be moved in any direction.
"These simple rules when put together created a huge amount of puzzle possibilities from one single blue line."
The foundations of the game are what makes it so enjoyable to play, and the language it uses mechanically was relatively easy to translate across the multiple platforms it released on.
So, after already creating multiple versions of the game, the team set about making a version for Sony's PS Vita.
"We'd already talked to Sony about bringing Stealth Bastard to Vita and PS3 before we started Deluxe, since they were fans of the free version," Biddle explains, "but it was during the development of Deluxe that we signed the deal to do the 3D updated version for PlayStation."
The team wanted to translate the game across, retaining the core, but also doing the Vita's OLED screen justice.
"The focus of the Vita and PS3 versions were to bring the game in line visually with the HD consoles," he says.
"The levels are the same levels that were released in the Steam version, but lots of improvements and bug fixes were made as a part of that process. We also released the Teleporter Chambers DLC, which to my mind are the best levels we created."
The story behind the birth of this DLC is a familiar one, with the teleporters themselves being a mechanic that never made the cut during the concept stages.
"Back when the game was a future spy game, there were handheld teleporters that could be thrown around," explains Biddle.
"When I stripped the game back, I didn't strip it fully back - I actually originally kept the teleporters in as the main mechanic. The game was going to be stealth with handheld teleporters. But when the level designers started trying to get to grips with the teleporters as a focus for the levels, it all proved too complicated, and a huge barrier to making enjoyable gameplay.
"When I realised this was happening, I took them out, and the game took its shape quite quickly. I always loved the interesting gameplay they created though, so when we did Deluxe we added in a lot of additional equipment as toys with which to play the game in different ways, and the teleporters were one of those toys.
"When we came to look at DLC, I wanted to revisit that initial concept of 'stealth with teleporters' and felt that - now we know the game inside out - we could do something amazing with them. So I tasked the designers with fleshing levels out based around the teleporters and the result is the Teleporter Chambers."
So, not only was the game once about a bounty hunter infiltrating facilities, but it was very nearly a 2D Portal, with stealth.
"The concept was definitely similar to Portal," admits Biddle. "But the teleporters are manual devices that are thrown around. The player moves them into places they can't get, and then manually choose to teleport themselves, or any enemy or movable object, between the two devices. It results in some quite amazing puzzles."
From the original concept, this was one of the only aspects to survive the cull.
"The game really became it's own thing after that point," he explains. "I find when designing a game you start with a load of ideas that you then remove until the game shows you what it is. The rest of the game's design is then a matter of listening to what the game is telling you it wants to be.
"Once Stealth Bastard had revealed itself as a quick-paced puzzle game, lots of features just weren't relevant - they didn't work with the game's core gameplay - but a lot of different ideas introduced themselves instead. The key is to know which to disregard and which to lean on or emphasise.
"That can really only be done by playing the game often, seeing others play it, and quickly changing a game to be ready to play again. Being a coder-designer helps immensely with this, since decisions can be made on the fly while working."
Something that did change along with the Vita release was the game's (oh-so British) name - Stealth Bastard: Tactical Espionage Arsehole - originally intended to be nothing more than placeholder:
"It was my placeholder name which I impulsively put down as the project name when I changed it from a future spy game to a stealth game," Biddle explains. "There were two things that I wanted the game to be: stealthy, and hard.
"Stealth Bastard was my literal placeholder name that I never expected to use. It did form a lot of the tone of the game, for example, probably making us highlight the irreverence we obviously hold for the player via the projected text, and generally influencing how we leaned on humour in the level design.
"I think if it'd had a more po-faced working title, it would've become a more po-faced game. Maybe."
Biddle says that, when it came to renaming the game for the free version, there was a lot of internal debate about what impact it might have.
"I wanted to change it for quite a while, but had to admit that the placeholder name had attained a certain 'punch' and people in the office had an affinity for it. in the end, we just couldn't think of anything we liked more, so we stuck with it and hoped no one would hate us."
When it came to the Vita version, the team decided that a more family friendly name was in order, however. As well as having to adhere to Sony's policies.
"The HD version was a good opportunity for us to take the game to a different audience with different expectations, and both Sony and us felt that a less profane name would suit a console release better," he explains.
"To be honest, while some love the name, it can be polarising. For every person who picks it up because it has an in-your-face title, there are people who will disregard it as being childish. The name has certainly done equal good and harm for us.
"I've had discussions with people on the Steam forums about having the game in their Steam library that their young children can see. It's not a binary issue, there are many sides to it - as a parent I can see that, and maybe the PlayStation Store is one of those places that should be free from profanity. It's not like you can age verify someone before they read your title.
"For some of the same reasons, we'll be using Stealth Inc for the iOS release. Apple do allow titles with swear words in them, but I tell you now, they won't feature them."
The original name is memorable, to say the least, but it's obvious how it could cause problems - especially the homage to Metal Gear Solid's tagline Tactical Espionage Action.
"It was the punchline to the joke," Biddle says of the game's original subtitle. "And it made people smile. It matches the tone of the game; it lets you know that you're not going to have a serious time with this title and its homage to metal gear says something about the games it is referencing.
"I mean this is an unashamedly videogame-y videogame. There are plenty of more worthy and artistic games around, and I love them, but this is a silly puzzle platform game that will make you laugh, and that's what the title highlighted really.
"Having said that, Tactical Espionage Arsehole was funny to me once, but jokes wear out their welcome pretty quickly. The first time you hear it, it may raise a chuckle, but after three years, well... I think I'd come up with something with more legs next time."
When making a stealth game, serious tone or not, it's hard to not take some inspiration from the daddy of stealth: Metal Gear Solid. And the homage spreads farther than a pun after the game's title.
"Metal Gear Solid was a very inspiring game for me and many other game developers back in the PS One days," admits Biddle.
"So it was definitely an inspiration. It was so successful that we could take its visual cues as shorthand for our own stealth language, and everyone would know what we were communicating.
"The question mark and exclamation mark symbols were 'borrowed' from MGS purely because I knew that pretty much every player had been taught already what they meant."
On the surface, it also looks like the game has taken some inspiration from Ubisoft's Splinter Cell series, too. From the paunch-bellied clone protagonist's goggles, to the way objectives are projected onto the wall. But this, says Biddle, is purely coincidence.
"I've only played one Splinter Cell game for a couple of hours myself - I've just never really got into them, he says. "The goggles design was nothing to do with Sam Fisher's goggles, it was pure functional design leading to a similar conclusion.
"The same happened with the projected text. I was aware that Conviction had used a similar thing, but I just wanted to offer tutorial text that didn't pause the game. I just messed around with a few effects until I found the projection style blend and really liked it.
"Later on, that moved from tutorial text to becoming a key part of the game's character, but no, not consciously referenced from Splinter Cell."
The projected text was a solution to a problem then, more than a homage to another stealth series. And, as the game was originally created as a means of creating problems to solve - a training exercise of sorts - this wasn't the only development hurdle.
"Development of the original 2D version didn't really have any difficulties," says Biddle.
"Since it was a long experiment that almost made itself. There were technical challenges, but they were just interesting hurdles to overcome, which was the reason I was doing the game in the first place.
"Doing Deluxe in three months was certainly difficult, since I had to code the game and also ensure that the other departments knew what they were doing, while also ensuring the game's quality.
"As I say though, with such a great team of talented motivated people as we have here, it was a pretty pleasurable time. The game was originally made in Game Maker 8.1, and for the Humble Bundle I had to move it to Game Maker Studio so that I could do Windows, Mac, Linux and Android versions.
"The two versions of Game Maker were so different that this was a major undertaking, and actually took longer than the original three month development. YoYo Games were brilliant during this time, offering hands-on support in helping me meet my deadlines. Great guys.
"Also, getting the shaders optimised for the Vita version of Stealth Inc was a pretty tricky task. The lights and shadow made the game run at around 50 percent speed for most of the console development, which was a serious concern.
"Again, the talented team we have here managed to do it in the end, but it was only in the last two months that the console version of the game actually played like it should."
Biddle notes that the forthcoming iOS version is also "proving to be a bit more intensive" than he'd hoped.
"The different screen resolutions and aspect ratios have meant creating three different versions of each of the game's 80 levels - iPad, widescreen iPhone and 4:3 iPhone," he adds. "Testing the iOS version of the game now means playing it through three times every time the levels are changed."
With the iOS version imminent, it won't be long before the game is available to an even larger audience. The team is now focused on making the controls feel right on the platform.
"I've never been a fan of virtual joysticks," admits Biddle, "but have always been curious to see if I could do something better than I'd previously seen - I should note I'm no virtual joystick expert, I rarely play games on my phone or iPad.
"I took my time to try something a bit different to the usual stick that sits underneath your thumb, and I think I've managed to do something pretty responsive, and close in function to a true console analogue stick.
Biddle notes that the people who've tried it have said they found it to be "up to the task" when it comes to controlling with precision the game's fast-paced platform action.
"I don't think you can ever please 100 percent of players with controls such as this, but I'm fairly confident that with practice you'll be fairly impressed," he claims. "I can get very similar speed run times on my iPad as I can on my 360 pad."
With regards to general performance on iOS, Biddle believes that more optimisation is in order before release.
"Performance of Stealth Inc on iOS isn't as good as I'd like," he says. "Since the game is reasonably complicated, and doing some complex things through Game Maker Studio's interpreted code. Our lowest spec is a 4S, which is in line with games such as XCOM and Bastion."
After the iOS version, the studio is going to be focusing on both development and publishing, so expect to see much more of Curve studios in the future.
"As well as our own development, we've expanded to become a digital publisher, having recently released Thomas Was Alone, Stealth Inc and Lone Survivor on PS3 and Vita.," Biddle concludes.
"We'll be releasing Proteus on the same platforms very soon, and have some other really cool titles in the pipeline.
"We also have our own games in development as always, the details of which should start being released some time next year. We've always been a creatively-led studio and that is not going to change. I'm pretty sure people will like what we're cooking up."