Ideaworks Game Studio on taking World At War: Zombies to the App Store.
UK firm Ideaworks Game Studios took to the stage at the Develop conference today to talk about its work on Call of Duty: World at War: Zombies for iPhone.
The developer worked on the game for Call of Duty franchise owner Activision, and it was based on a bonus game in Call of Duty: World at War for console.
In early 2009, Activision and the console game's developer Treyarch started mulling taking it to iPhone, but Clarke says they faced questions about how to adapt it - not least because there were few good examples of first-person shooters on the iPhone.
"We weren't really sure how we could be fairly certain of success," said Clarke. "It didn't really follow at that time that having a big brand would automatically succeed [on the App Store]."
He also showed a graph of chart positions for games like Grand Theft Auto: Chinatown Wars, The Sims 3 World Adventures, Sonic 2 and Street Fighter 4, showing how initial big sales spikes quickly decline on Apple's store.
"They fall off quite quickly," he said, pointing out that casual iPhone games are much more consistent performers on the App Store - think Doodle Jump, Bejeweled 2 and Flight Control as examples.
"Their success keeps on rolling, and the buzz sustains," said Clarke. "We intuitively understood the importance of trying to get casual game appeal into this game [Call of Duty: World at War: Zombies] even though it clearly wasn't a casual game."
Clarke talked about the design challenges for bringing the game to iPhone, starting with the control issue - how to get people running, looking and shooting on a touchscreen with no buttons, analogue sticks or triggers.
Ideaworks did some research into how people hold their iPhones, and came down to two main ways - in one hand with the other hand's fingers touching the screen, or in both hands and tapping the screen with thumbs.
Of course, there's something else - an accelerometer - which can be used in theory for movement.
"When we tried this out, not only was it impossible to use, but it also made people feel sick!" said Clarke. "It was always going to be something with a learning curve that a lot of people would not have the patience for."
Ideaworks went for the two thumbs approach in the end. Clarke also talked about putting multiplayer features into the game, since they are so core to the Call of Duty games on console. However, at the time the iPhone game was being developed, this seemed like a "quantum leap" for the technology.
"I wouldn't really recommend doing it if I'm honest," he said. "We didn't have a choice..."
Why? Because there are so many variations and factors to deal with - different routers, latency, bandwidth... things that can't be modelled in a lab, but have to be tested out in the real world.
Ideaworks spent a lot of time squeezing down the game world and graphical detail for iPhone, while aiming to retain the original feel and experience, and the sense of 'quality' that was so important to Activision. The game was successful, staying in the US Top 10 Grossing chart for five months, and got a 4.5-star average review score on the App Store.
"We managed to capture some of that casual sustainability," said Clarke. He said making this kind of game now is a bit more complicated, since the iOS platform is fragmented - "there are more variables to take account of" due to fragmentation of the platform: iPad's larger screen, iPhone 4's high-res display and gyroscope.
However, Clarke said the core concepts behind taking this kind of game to iPhone remain the same now. He was also asked about updates to the game.
"We didn't really cotton on to that until later than we should have done," he said. "We took the decision quite early on not to rebuild the levels - we tried to stick closely to the original thing, so our roadmap was set up in front of us."
However, Ideaworks did follow feedback on forums - one famous bug in the multiplayer mode was related to people playing through BT home broadband hubs - and try to act on it.
Clarke also said it's difficult to tell what proportion of the iPhone game's players were existing Call of Duty players from console, and what proportion were new to the franchise.