Introduction/Background Interactive computer play (ICP), or serious games, can provide motivational and flexible rehabilitation environments. This is useful for the 1 in 400 children born with Cerebral Palsy (CP) each year, whose daily activities are impacted by impaired motor control. Improvement through traditional rehabilitation is often hindered by low adherence and limited repetitions. This study aims to build an ICP game which offers a motivational and effective environment to supplement reaching and grasping rehabilitation in youth with CP. Material and method Through a user-centered design process, we first met with five youth with CP and four occupational therapists to establish reach and grasp movement priorities. Then, seven youth, age 16–23 years with hemiplegic CP, participated in 1–3 game design sessions. During each design session, participants extended and relaxed their hand to control an ICP game using a forearm muscle activity sensor (Myo Armband). Participants played games with different types of feedback and control mechanisms (detailed in Fig. 1). Game versions were iterated between design sessions. Results The top priority identified by youth and therapists was increasing amplitude and endurance of wrist extension while fingers open. Thus, this action was used as the primary game control. At each design session, participants played an average of 15 levels, each lasting 129 ± 56 seconds and requiring 43 ± 19 wrist extension repetitions. In total, during a typical session, participants practiced 645 ± 285 repetitions through the ICP game. User input showed participants were most responsive when feedback directly followed wrist extension (e.g. increased power bar or bonus points). Conclusion The user-centered design process engages participants to build practice tools that they find motivating. The ICP game can offer youth with CP the high quantity of repetitions required to improve reach and grasp activities. Next, the game will be used in a home-based pilot study to demonstrate its efficacy for improving reach and grasp activities.