A picture of a hand appears in different positions and rotations. Decide as quickly and accurately as you can whether it is a left or a right hand — tap the buttons or use your ← / → arrow keys. Your brain briefly “tries on” the movement to judge the side; training this restores a clearer body map, the first step of graded motor imagery.
It is a practice and progress-tracking aid, not a diagnostic test. Work in short, regular sessions and watch your accuracy and speed over time. As a rough benchmark, typical adult performance for hands is around 80% accuracy with ~2-second responses and similar left- and right-hand results (NOI reference). Your results stay on this device.