Inclusion Criteria:  aged 16 to 24 years old (inclusive) currently based in the UK possess a basic literacy in English able to provide informed consent reporting elevated levels of worry and rumination, defined here as scoring above the 50th percentile (i.e., top-half of scale) on either the RSS (>34) or the PSWQ (>41) have regular access to a smartphone (android or iOS).  Exclusion Criteria:  reporting highly elevated symptoms of depression indicating more specialist treatment is required (PHQ-9 > 20) self-report of active suicidality self-report currently receiving psychological therapy, counseling, or psychiatric medication, including antidepressants, for a current mental health condition