For nearly two decades, immersive Virtual Reality (VR) has been used as a form of pain distraction and management for acute, chronic and cancer pain. Moreover, in numerous studies, VR games and virtual environments (VEs) have been shown to be effective during chemotherapy treatment for reducing pain and anxiety. However, amongst all of these research studies, few have focused on pediatric patients who are undergoing chemotherapy treatment. Furthermore, most of the research studies used commercial video games which were neither specifically tailored for immersive VR environments nor for pediatric patients. Therefore, to understand pediatric oncology patients' preferences about using specific VR games during their treatment, we developed a VR farm simulation game called Farmooo using an Oculus Rift DK2 and a Leap Motion sensor. In this paper, we introduce the design inspirations, rationale and procedures, as well as the game mechanics of the VR game we specifically built for this application, entitled Farmooo. Our goal was to design and test a VR pain distraction game that will enable our future participants to immerse themselves in the game world and thereby help to distract them from their pain and discomfort during and after chemotherapy. Results from our pilot Focus Group study with pediatric outpatients showed the great potential of the VR game, Farmooo, as a distraction tool.