One in 500 Canadians has cerebral palsy (CP), a lifelong condition affecting movement and function. Physical and occupational therapies greatly benefit children with CP but can be costly and difficult to access. Children, parents, and clinicians are interested in using movement-tracking video games for home-based hand/arm therapy. Yet, the technologies and evidence to support this approach are limited. We partnered with key stakeholders and an interdisciplinary team to co-create Bootle Blast. Bootle Blast tracks skeletal movements and interactions with real-life objects, engaging children in individualized play experiences rich in feedback, task specificity, and opportunities for goal-directed motor practice linked to meaningful activities. To establish Bootle Blast's clinical effectiveness, a large-scale randomized controlled trial (RCT) is needed. Pilot RCTs provide important insights that position large-scale RCTs for success. As a result, the goal of this Pilot RCT is to test whether a mixed-reality video game intervention (i.e. Bootle Blast) can improve upper-limb function, activity, and participation in children and youth aged 6-17 years with hemiplegic cerebral palsy. The main questions it aims to answer are: (1) Is it feasible and acceptable for families to use Bootle Blast at home for 12 weeks? (2) Does the intervention show preliminary improvements in hand-arm motor outcomes compared to usual care? Researchers will compare an immediate Bootle Blast intervention group to a waitlist comparison group that continues usual care for 12 weeks to see whether access to Bootle Blast leads to increased practice, greater engagement, and improved motor outcomes. Participants will: Complete three in-person assessments (baseline, 12 weeks, 24 weeks) with standardized motor and participation measures. Be randomized to begin 12 weeks of home-based Bootle Blast immediately or after a 12-week waitlist period. Use the Bootle Blast game at home for 15-20 minutes per day, 3-4 days per week, with all gameplay tracked automatically. A subset of participants will also receive weekly 10-minute support calls from a monitoring coach.