The popularity of casual Facebook game Criminal Case is due to the team devoting a huge chunk of development time to creating a compelling opening gameplay experience and simplified invitation system, according to the game's creators.
During a presentation at GDC Europe 2013, Pretty Simple Games' co-founders Bastien Cazenave and Corentin Raux said the game has grown to 9 million daily active users since it launched in December 2012. This growth was possible due to a number of factors, one of them being Pretty Simple's dedication to tracking player clicks and designing an easy-to-use system for players to invite their friends.
One way to assure player retention is to design a compelling experience for the beginning of the game, according to Raux; great "opening sessions" are key to drawing players in. Successful first sessions mean new players will send out invites via Facebook to their friends, which in turn can result in the addition of more players. Developers must also make sure games are easy to learn and that tutorial sessions aren't so dense they lose players' interest.
In Criminal Case, players solve crimes by completing puzzles and hidden object challenges. Every week Pretty Simple launches a new investigation, which players can work together to solve. Raux said that the key to bringing more players into the game is to reward players for inviting others, especially when they send out invites close to when they first join.
After the first gameplay session in Criminal Case, players are given the opportunity to earn free in-game currency by inviting their friends to play. By making this action easy — pre-selecting all Facebook friends on the invitation screen and allowing the invites to be sent by clicking one button — players are more likely to send out the invites, according to the developers.
People come back to Facebook games because they get requests from other users — such as notifications for other players' needing in-game currency — or other communications from the games, said Cazenave. Invited friends who join the game can then send the player who invited them free in-game gifts to help solve investigations. Cazenave said that the day one retention rate for Criminal Case is 52 percent, which he says means it has had successful "virality," or spreading through word of mouth.
"You can't have retention if you don't have virality," Cazenave said. "Try to focus first on that virality [of the game] and then retention."
Criminal Case is currently available on Facebook, and will launch on iOS sometime next year.