In this work we propose to apply a participatory design process for developing mobile games focused on learning and communication of autistic children. This study employs a game to help people with autism and describes the complete design process used in this research. As a result of the design process was possible to note the necessity to allow high customization and personalization of digital activities in order to promote the user engagement and gameplay ability. Moreover, more details are provided about the developed game. Two customized interactive activities were developed: Questions & Answers and the Emotional Thermometer that were evaluated with therapists, autistic children and HCI specialists. Finally, it is described the importance of therapists in game design process and the requirements for redesigning the application interface.