Pressing this asks your browser for camera access. The video frame is read directly by a face model that runs on your device. No frame or landmark is ever transmitted — the page-level policy above refuses any request that isn't to this same site, so nothing here has anywhere else to send it.
Also downloads the face model, served from this site and cached by your browser afterwards.
Calibrate your gaze
Look at the highlighted point below and press "Capture this point". Five points, one at a time, map your own comfortable range of eye movement to the paddle track.