Call of Duty's zombie-fueled move to mobile devices

Activision’s Call of Duty series showed its dominance in the console space for this entire console generation, as it successfully made the transition from a reverent World War II shooter to a melange of explosive modern-era war set-pieces. However, tucked away in Call of Duty: World at War (and made much more prominent in Call of Duty: Black Ops) was a certain Zombie Survival mode that surprised and entertained many Call of Duty fans worldwide. It was that mode that allowed Activision and Ideaworks Game Studio to bring the Call of Duty series to the mobiles, most recently with Call of Duty: Black Ops Zombies. Black Ops Zombies follows the successful release of 2009’s World at War Zombies on iPhone, a game which had surprisingly long legs according to Rob Hendry, studio head of Ideaworks Game Studio. "We had high hopes, but we have been surprised and humbled by the sustained level of interest and goodwill towards the game," he said. It would be easy to conceive that some form of Call of Duty on iOS should be a given due to the success of the series on consoles. As it turns out, however, there was some convincing to be done. Hendry gives credit to Treyarch studio head Mark Lamia for helping champion the idea in its early stages, and Activision producer, Jason Harris for helping with co-ordination and communication to keep the project moving. After the wheels on the project were spinning, Ideaworks -- with consultation from Treyarch -- was left to make the game which, as Hendry stressed, was rebuilt from the ground up, not ported. "The engine and game logic are entirely created at Ideaworks, building on our Marmalade SDK and our higher level game tech libraries. The mobile-optimized game assets are created by hand, using the originals as reference," said Hendry. "The game design is original work, created for mobile after studying and learning the game inside-out, in order to make decisions about where to simplify, adapt or diverge. "Of course, a lot of mechanics are similar in the end, but everything has to be rebalanced for mobile. It can be surprising how much has to change in order to make something feel like the original!" Despite the original's success, there was still plenty of room for improvement and refinement for last year’s Black Ops Zombies, with the team deciding to focus on enhancing multiplayer features like voice chat, and making the game accessible to more devices to help expand the player base. "We saw, from anonymous usage stats in World at War Zombies, that there was a large segment of devoted gamers who really want to get involved but don’t have the latest hardware," said Hendry. "Seeing this, we avoided the temptation to focus on the latest device generations and tried to deliver a smooth and high-quality experience across all the GLES2-compatible devices, right back to the 3GS and iPad." In addition to multiplayer improvements, changes when moving from World at War Zombies to Black Ops Zombies were implemented to "take Black Ops Zombies to the next level and build on the success of the original game." These included an improved collision system, AI and path-finding. With iOS titles such as Backbreaker Football: Tackle Alley and Resident Evil: Degeneration under their belt, Ideaworks Game Studio is familiar with bringing console experiences to handheld devices, but fully recognizes that they can’t compete with what’s available on more high-end machines. "Our 3D engine is good, but it can’t compete with an Xbox 360," said Hendry. "So we have to heavily optimize geometry and texture detail, as well as simplifying animations. Automated asset-optimizers typically do a poor job, so we rely on the experience of our art team to judge where detail matters and must be preserved, and where it can be removed with little or no perceptible impact." Similar optimisation principles also apply to other areas of the game, namely its physics and AI, where "The complex simulation of the original game would not be fully appreciated on a small screen or tablet device, where usage patterns typically favour short bursts instead of long play sessions, so we simplified simulations, optimizing them for the processing power of mobile devices." Ultimately, though, it all comes down to the user experience, where interaction is key. Here it’s not a matter of optimising existing tech or simulations; the game’s interactive elements are completely re-designed. "Simplicity is paramount in creating an engaging touch-driven experience, so we identify which user interactions are core to the experience... and focus the design around those. Less central functions may be simplified or even removed; for example, jumping is not essential to Zombies gameplay, so we took that out."