Three tests neurologists use at the bedside, rebuilt for a webcam and a touchscreen. Tap your fingers, hold your hand out, draw a spiral. The page measures speed, rhythm, fatigue and tremor frequency, then explains what the numbers mean.
A demo, not a diagnosis. These are simplified versions of real clinical tests, measured with an ordinary webcam. Tiredness, caffeine, cold hands, lighting and camera angle all change the numbers. If you're worried about a tremor or slowness, see a doctor.
Methods follow the tests' clinical versions in spirit: finger tapping from the MDS-UPDRS motor exam, postural tremor frequency bands from movement-disorder research, and spiral analysis from Archimedes spiral studies. Checked against simulated hands: tapping rate within 0.2 taps/s, tremor frequency within 0.1 Hz. Webcams run at about 30 frames a second, so tremor above about 14 Hz and shake under about half a millimetre can't be seen.