The ACE of Hearts Serious Game for Young People With Adverse Childhood Experiences: Experience-Based Co-Design and Agile Development Study.

Background: Young people exposed to adverse childhood experiences (ACEs) are at risk of poor mental and physical health across the life course, yet many struggle to access timely help. Serious games offer an engaging, scalable, and stigma-reducing support, but few are co-designed with young people who have lived experience of ACEs, and methodological accounts of how participatory design is operationalized alongside software delivery are scarce. Objective: We aimed to (1) develop and apply a novel methodological framework integrating experience-based co-design (EBCD) with agile game development to co-design a serious game with young people affected by ACEs, (2) describe the co-designed game prototype and the design decisions shaped by youth participation, and (3) examine the ethical and safeguarding considerations arising from co-designing digital mental health interventions with trauma-exposed young people. Methods: We conducted a participatory co-design study comprising 12 workshops across 8 iterative co-design sprints, involving 18 diverse young people (aged 12-24 years) with lived experience of ACEs, 5 professional stakeholders, and a multidisciplinary game development team. Young people were recruited across England through partner youth organizations and regional Young People's Advisory Groups. Co-design ran from June 2022 to April 2024 in hybrid and online formats. Baseline characteristics include demographics, and mental health and well-being measures. EBCD activities were mapped onto agile practices (sprint planning, sprint reviews, and retrospectives); all feedback was logged in a "you said, we did" form. Analyses were descriptive, and reporting followed the GRIPP2-LF (Guidance for Reporting Involvement of Patients and the Public, long-form) checklist. Results: The resulting prototype, ACE of Hearts, comprised a central "cozy den" hub and 4 mini-games addressing bereavement and caregiving, trauma and disability, gender dysphoria, and poverty. Youth feedback directly shaped 47 documented feedback and design decisions. Co-design participants (14 of 18 participants) were diverse in gender (8/14, 57% men or boys; 3/14, 21% women or girls; 1/14, 7% nonbinary; 2/14, 14% another identity; and 3/14, 21% transgender), ethnicity (5/14, 36% from minoritized ethnic backgrounds), sexuality (6/14, 43% bisexual or pansexual), and neurodivergence (7/14, 50% autistic), with elevated levels of depression (mean Patient Health Questionnaire 9-item scale 8.8, SD 4.5) and anxiety (mean Generalized Anxiety Disorder 7-item scale 8.4, SD 3.9). Mean posttraumatic stress symptom severity (Children's Revised Impact of Event Scale, 8-item; n=13) was 22.5 (SD 7.7). Design innovations included metaphoric storytelling, integration of narrative exposure therapy principles into gameplay, and an embedded ethics framework addressing representation, agency, and emotional safety. Conclusions: Integrating EBCD with agile development is a feasible and transparent method for coproducing trauma-informed serious games with young people who have lived experience of ACEs. The approach is transferable to other participatory digital-health projects involving vulnerable populations. Future work would evaluate acceptability, feasibility, and clinical outcomes.