Cross-platform gaming offers a lot of opportunities, but it's very hard to retrofit web games to mobile.

That was the starting point for Kabam co-founder Michael Li at the Free To Play Summit at GDC 2013 in San Francisco.

Entitled From Click to Tap: Building Kingdoms of Camelot for Mobile, he spoke about how Kabam approached bringing its successful Kingdoms of Camelot web city-building PVP game to mobile.

As the existing web game had a big code base that wasn't designed for mobile, and the development team for the original games was in US while the mobile team was in China, Kabam decided to create a standalone iOS and Android game based on the web game.

Ch-ch-changes

Of course, while the mobile game has a lot of similarities, the important things were the changes.

For example, the combat system was simplified, and some other elements changed because Kabam couldn't figure out how to get the UI for those systems to work on mobile.

More generally, user experience was a key issue.

"We focused a lot on players first and second sessions," Li said. "You don't see a loading spinner in the game, even if you can't get a good connection."

This happens because a lot of the connection requests between the game and the server happen behind the scenes, with various assets downloaded in the background to improve the gaming experience. Kabam also optimises package size and rework networking to support socket and HTTP requests.

"We're used to thinking about these games as being server-centric but with a mobile you have to use it as computer not just a browser," Li said.

QA, QA and QA

In web, the tendency is to push the game out and let your users do the QA. Not on mobile though.

"There's no such thing as a rollback on mobile," Li said. "When you submit to the App Store, your code has to be as perfect as possible."

In this way, Kabam does a lot of A/B testing, what Li called A/B/C/D testing. It also builds a lot of kill switches into its mobile code so it can control the user experience.

The end result of this approach, combined with the review period for the App Store, this meant the mobile team's dev cycles have become much longer than those of the web team.

Another interesting difference is that mobile users tend to consume game content quicker than web, because committed players can play 24/7 on mobile if they want to.

"[Mobile] Users are smart. You have to make your game for mobile. You can't just port your browser game," Li concluded.