Guerilla Cambridge, formerly known as SCEE Cambridge, brings a fresh set of eyes to the Killzonefranchise.

Previously, the studio has worked on multiple IPs, including MediEvil, LittleBigPlanet, Heavenly Sword and Primal to name but a few. It then found itself merged with Guerilla  the outfit behind Sony's flagship Killzone series - at the beginning of 2012.

The studio's first task wasn't so much a case of dipping their toes in the water, however. Rather, the newly branded Guerilla Cambridge had to dunk itself in, face first, bringing the Killzone franchise to handheld.

"It took us a while to convert the Killzone 3 engine to work on the PS Vita," Mark Green, senior producer at Guerilla Cambridge tells us. "And then actually pulling the game together was probably a little under two years of production."

Shadow fall

The concept behind Guerilla Cambridge's Killzone: Mercenary was born not only from a willingness to bring the IP to a portable platform, but also out of a desire to explore the narrative away from the shadow of the main series.

Senior producer Mark Green and lead designer Gareth Hughes

"The genesis of the Mercenary concept was really driven by the teams' interest in exploring the narrative relationship between the Helghast and the ISA," says lead designer Gareth Hughes.

"Showing that it was more nuanced than simply good guys versus bad guys.

"With the player taking the role of a mercenary and working for both factions, they are able to see that both sides are essentially willing to commit horrendous actions in pursuit of victory.

"The Mercenary theme also gave the opportunity for the team to develop mechanics and systems new to the Killzone series. A good example of this is the VAN-Guard system."

In the final game, although showing the player both sides of the conflict, the narrative was strictly linear. That's not to say the developers didn't consider allowing the player to choose their missions, much like a mercenary would.

"The idea of the player choosing their contracts and their affiliation was something we were really interested in," admits Hughes. "But was simply beyond the scope of this project."

"We didn't have to make any omissions due to the platform. Our remit was to create a fully featured Killzone experience on a handheld device, so right from the very early concept phase we were unwilling to omit anything we felt would compromise this goal.

"If anything, working on the Vita opened up new opportunities."

However, just because there weren't any omissions due to platform choice, that didn't mean that player choice was the only idea left on the cutting room floor.

"Two features stand out as things we really wanted to do but simply ran out of time to implement to a standard we were happy with," continues Hughes.

"We designed an asynchronous challenge mode, where a player could take a campaign mission and then choose from a set of criteria to create additional objectives, and then issue this as a challenge to other players - allowing them to take part even if they weren't online at that time.

"The second feature was support for bots in multiplayer. We recognise that this is something that players really want to see in the game and, if possible, we would really like to add."

In for the kill



Speaking of the multiplayer, the team had the lofty task of recreating a triple-A online experience on the handheld console. Key to achieving this, was balancing. Lots and lots of balancing.

"The multiplayer was balanced over many, many hours of playtesting both in the studio and externally through several Beta trials," explains Hughes.

"One of the biggest challenges we faced was the unified economy across single and multiplayer. Because of this feature, we had to make sure that the earning rates in both modes were contributing the same amount of money over a period of time.

"This was critical to the Valour system, as it relies on the player earning rate when issuing their Valour Card and we had to ensure that players playing single player mode were not able to earn more that players playing multiplayer or vice versa."

Hughes notes that the team chose to make the entire weapon set contextually balanced "rather that have unlocked weapons get progressively more powerful than the last, this meant that all weapons needed to have a useful role."

He continues, "Another self-imposed balancing challenge was that we wanted the weapons and equipment to feel the same in both single and multiplayer. So if a player uses a weapon in multiplayer it will have the same damage and handling characteristics when used in single-player."

Because of the platform of choice, the team also decided that four vs four was a perfect fit for Killzone: Mercenary. This was a conscious design decision, rather than a restriction of the platform.

"The four versus four player count is a design decision, not a hardware limitation," reveals Hughes.

"The reasoning behind why we decided to support that number of players was both technical and practical. Technical in terms of being unwilling to compromise the visual fidelity of the game in order to support more players and therefore bigger maps, and practical in wanting to fill lobbies quickly."

Another thing the team wanted to work identically across the single and multiplayer portions of the game was the score system, which gives the player money for almost every action across both portions of the game.

Again, balancing these so one mode isn't preferable to the other for a grinding player, was a priority for the studio.

"Core to the Mercenary concept was the idea of unifying the progression across single and multiplayer," Hughes explains.

"In order to achieve this we needed a unified economy and the obvious choice, being as you play as a mercenary, was cash.

"As we developed the progression system, we found that using money as a reward not only fitted really well with the Mercenary theme but also made things very easy for the player to understand, creating a classic; action, reward, spend, new action loop.

"We also leveraged the cash-based economy to create a non-linear competitive ranking system, which we called Valour. This system essentially awards all players a card or rank based on their earning rate when compared with all the other players in the community.

"The benefit of this system is that the highest ranked players are always the players who are performing the best in the game on any given day."

Shifting perspectives

These decisions - whether the player count, or in balancing the weapons to be identical across all modes - have all been solutions to recurring design problems. And, like in all games development, these issues weren't isolated.

To identify the biggest problem, Hughes says, would depend on who at the studio you happen to ask.

"From a technical point of view, maintaining a stable and acceptable frame rate while supporting the level of visual fidelity we wanted to achieve required a huge amount of optimisation of both engine and assets," Hughes explains.

"This optimisation wasn't as straight forward as simple poly reduction and texture sizes, we had to optimise some core parts of the engine and the design of the missions themselves were tailored to be as efficient as possible.

"In terms of the overall production, our biggest challenge was really to try and meet the incredibly high level of expectation of what a handheld version of Killzone should be. Very early in the project our mantra became 'to make the best portable FPS ever'; we'll leave it to the players to decide if we delivered it."

Guerilla Cambridge's art director Tom Jones had an altogether different problem to solve, of course. It's all a matter of perspective.

"Throughout the project we were very mindful of enemy visibility," Jones explains. "Finding a way to get the NPCs to stand out across a variety of environments, as well as in a fully functioning multiplayer scenario was particularly problematic.

"As well as trying to ensure that key targets were backlit, we also spent a lot of time iterating on the character shaders to make them stand out more. We ended up pushing the rim lighting, particularly on the lower lods to get the enemy soldiers to pop.

"We actually created slightly different versions for multiplayer where this effect was boosted even more."

Art director Tom Jones



That's not to say the smaller screen always made development more difficult, however. The smaller screen, and the fact that all players are looking at the same thing, also had its advantages.

"One of the biggest advantages is knowing that everyone is going to see the game the way you see it," Jones continues.

"There is no need to worry about visual fidelity on a variety of different TVs with different settings. The downside is that when we wanted to do group reviews of the art, we ended up having to use TVs a lot just so that everyone could see.

"This obviously carries inherent risks as it wasn't indicative of the true experience. This was compensated by key leads reviewing the game constantly on the Vita."

The tools the studio used to achieve this task were - for the most part  proprietary, developed alongside the Killzone Engine.

"We have a custom built Asset Database that manages the majority of the content needed for level production," explains Jones. "This is fully synced with Maya for ease of use for artists.

"We also have a custom built node based editor that is used a lot for providing the filmic post processing passes; contrast & distance based level balancing, colour shifting, fog ranges, etc. All very powerful, and very important in helping us achieve the signature Killzone look."

And that look is a big part of the draw for franchise fans. Killzone has always been a game used to showcase Sony's hardware. As such, the team wanted to do that legacy justice on the Vita.

"The Killzone franchise is known for its gritty, immersive, high fidelity worlds," Jones admits.

"We felt that Mercenary wouldn't be seen as a Killzone game if we didn't achieve this. One of the opening experiences in the single-player campaign, is an in-game wingsuit glide through a futuristic city. This was our way of saying, look, this may a handheld game, but it is still epic."

Fortunately, the team were in luck when it came to mimicking the style of the game's older brothers. The Killzone assets were - for the most part - available to recycle and repurpose for this scaled down version.

"We recycled a lot of assets," Jones says. "Poly-wise, the Vita versions stand up pretty well to their KZ3 counterparts. However, we had to be really aggressive with UV layouts and Lodding to minimise total texture memory, and to reduce the amount of tris drawn at a distance."

Hearing the one that kills you

When trying to squeeze a PlayStation 3 game onto the Vita, though, sexy graphics alone won't do. Just as important, when immersing the player in a first-person world, is sound design.

Audio manager, Jordan Pedder, was the man in charge of making this happen.

"The sound design for Killzone mercenary was something that had to be approached in two stages," Pedder explains.

"The first stage would be recognising the iconic. This was very much an exercise in calling out which sounds are key to the Killzone universe and respecting that initial sound IP. Part of the core sound design and most immediately obvious group, are the weapons.

"The classic ISA M82 or Helghast STA52, have remained very much an integral part of the game series from the _Finaloutset, so it was imperative that these stayed true that experience.

"The Helghast voice processing is also very much a fundamental part of the audio. Not only a creative decision to make them sound more menacing, but it also serves as an indicator to the player of the direction and distance of the danger.

"The last area and probably not so recognisable would be the Kill Chirrup. A staple sound since the first in the franchise, but this has more than become an iconic piece of sound design.

Audio manager Jordan Pedder

"The second stage was carving out our own Identity. Once we have set out what sounds we need to keep, it will give us an idea of which areas will allow us to create a distinct identity for Mercenary. The three areas we concentrated on were, HUD sounds, new weapons and music.

"Walter Mair, our composer, did a fantastic job, creating a new music for the franchise that really complimented the gameplay. depending on which faction was your client, the music would reflect this employing orchestral elements for the ISA and more of a synth based approach for the Helghast."

With the Vita being touch screen, the new VAN-Guard weapon set was designed take advance of the systems capabilities.

"The idea of the VAN-Guard being a battle-worn piece of tech used by the mercs, a mix of HUD based 'touch sounds' and the weapon firing itself, really gave us the chance to stretch our legs and bring the system to life," he continues.

"Many of the sounds heard in mercenary are used throughout the series but the real identity comes from those based around the design of the Vita and what we can do with it as game designers."

Killing touch

Of course, the visual and sound design wouldn't mean anything if the gameplay didn't stand up.

It's a good job, then, that critics quickly dubbed Killzone: Mercenary as the best example of a functional FPS yet seen on a handheld  including Pocket Gamer. It isn't perfect, however.

The cover system in particular can feel a touch fussy, with the player popping up and down like an overzealous meerkat, depending on the height and proximity of the cover in front of them.

This, in fact, is the result of a solution to another problem that arises when designing a game of this scale.

"We wanted a cover system that would allow for the player moving through combat encounters in a fluid and progressive manner and would be supportive of more aggressive play styles," says game director Piers Jackson.

"Moving away from a traditional lock-on cover system provided the level of fluidity in combat we were looking for. However, the lack of a physical barrier that locking-on provides may result in the behaviour you are seeing.

"We felt that the lack of hard lock-on was a good trade for the removal of a button press to unlock from cover, which can feel slow and cumbersome."

In our time playing, we also uncovered a potential exploit where the player can create their own checkpoints mid-battle. This can be used anywhere where the game allows the player to use one of the various armament shops dotted around - buying from them triggers a checkpoint.

Again, this was a solution to an issue that reared its head during testing.

"When we first implemented the Blackjack armouries [the game's shops] without checkpoints we found, through user testing, that players got very upset if they made a purchase and then died and lost the purchase," Jackson explained.

"When we added the checkpointing to alleviate this issue it created the opportunity for players to force a checkpoint to occur."

Game director Piers Jackson

Outside of the checkpoints, though, if you decide to power down your Vita, you will find yourself back at the start of the chapter. Guerilla Cambridge decided that mid-mission saves weren't something that the Vita needs because of the capabilities of the hardware.

"We never really saw this feature a being essential as the Vita has such an efficient sleep system," reveals Jackson.

"The save system actually does save some aspects of your progression through the mission. Every time you checkpoint, the game saves your stats and earnings, so even if you quit the mission you still retain these."

The imperfections present in the game are, to an extent, the lesser of two evils. An entirely smooth road through the design process rarelty exists and often the only solution is to iterate and see what works.

However you view Killzone: Mercenary, as a technical feat alone its achievements are undeniable. Despite the device's continued struggles at the tills, on a creative level, PS Vita is a platform entering its prime.

With Killzone: Mercenary serving as the 70-strong Guerilla Cambridge's first Killzone title and, indeed, first Vita title, you could say all sides are just getting warmed up.