Abstract
BACKGROUND: Digital cognitive-behavioural therapy (dCBT) has been shown to be effective for anxiety and depression, yet sustaining engagement remains a key challenge that limits real-world impact. Gamification and extended reality (XR) elements may support motivation and skill transfer, but few interventions integrate these features within a clinician-compatible, clinically grounded framework. My Cosmos is an internet-delivered, mobile-first transdiagnostic dCBT programme that embeds first-wave CBT alongside selected second- and third-wave approaches within a game-inspired structure designed to support adherence and self-regulation. METHODS: My Cosmos was developed through evidence mapping, co-design with potential users and mental health professionals, iterative prototyping, and implementation of GDPR-compliant pseudonymised data flows. The programme assigns users to Anxiety, Depression, or Mixed tracks based on baseline PHQ-9, GAD-7, and SF-36 scores. Each track follows a six-module CBT pathway enriched with gamified Rehabilitation Objects and supported by a secure clinician web dashboard to enable blended care. Preliminary usability and acceptance were assessed through participatory workshops with university students (N = 124) and mental health professionals (N = 19), using standardised questionnaires (SUS, MAUQ, UTAUT2) and inductive qualitative analysis of open-ended feedback. RESULTS: Help-seekers described My Cosmos as intuitive, engaging, and emotionally supportive, emphasising its usefulness for self-regulation and structured reflection. Mental health professionals reported more moderate but overall positive evaluations, recognising the platform's value for supporting homework, monitoring progress, and enhancing continuity between sessions, while highlighting the importance of clear onboarding, transparent communication about data protection, and flexible clinical integration. Both groups converged on a blended-care positioning in which the programme complements, rather than replaces, the therapeutic relationship. CONCLUSIONS: This paper presents the development, clinical protocol, and early-stage usability evaluation of My Cosmos, a gamified, modular, transdiagnostic dCBT programme implemented within a secure digital environment. Findings inform ongoing optimisation and support progression toward beta/feasibility testing and a planned randomised controlled trial to evaluate clinical effectiveness, engagement, and health-economic outcomes.