Figure 2. A view of OpenButterfly gameplay. The protective transparent blue orb is outlined in white. The purple arrow shows the next incoming crystal cluster that heads towards the butterfly. To earn points, users need to place the orb over the butterfly to protect it from the crystal. Each crystal that is blocked earns a point

From

OpenButterfly: Multimodal Rehabilitation Analysis of Immersive Virtual Reality for Physical Therapy

Michael Ora Powell, Aviv Elor, Mircea Teodorescu, Sri Kurniawan

American Journal of Sports Science and Medicine. 2020, 8(1), 23-35 doi:10.12691/ajssm-8-1-5