RealEye-io/webcam-eyetracker-light-open — reverse-engineered prompt

Build me a browser app and reusable library that can do webcam eye tracking on a normal laptop or USB camera and give me on screen gaze coordinates. I want it to run fully in the browser, locally on the device, with no server needed and no special hardware.

Please include a polished demo page where the user first sees a Start Camera button, then a camera preview with face detection, then a 17 point calibration flow, and after that live tracking with a gaze cursor, trail, and basic session stats. Add helpful status messages like not ready, ready for calibration, and tracking. It would also be great to have webcam selection, a simple settings panel, and a diagnostics view so I can see what the tracker is doing. If someone opens it on mobile, show a warning that desktop works better.

Also expose a simple library API so another app can initialize it, calibrate from samples, and predict gaze from frames. Use the current docs if you need to fill in any gaps.