Working in teams is a common approach to solving problems. However, new teams often suffer from a form of cold start, by which individual members are not yet comfortable expressing their ideas. Previous work has shown that ideation can be stimulated by promoting a sense of psychological safety among team members and instilling an ambiance of openness, and that games are helpful at establishing such social bonds. However, most such games only partially target psychological safety or openness, and often rely on the expertise of a facilitator, who may be unavailable for many teams. The ubiquity of mobile platforms opens up many opportunities for overcoming such drawbacks. We developed the mobile game Grapplenauts, a novel serious game directly focused on psychological safety and openness, that generates a beneficial atmosphere for ideation and does not require any facilitator. In Grapplenauts, team players have to gradually work together towards a team-wide goal, first in pairs and then among pairs, which has shown to be quite successful in promoting communication and collaboration. Play testing has shown that Grapplenauts was perceived as a fun, engaging and challenging collaborative game. In addition, results of a preliminary user study are cautiously optimistic about the success of the game in improving the perceived atmosphere within
newly-formed teams.