Precision in an online task?

Scroll down and click in the demo space to try it out. Try to click where the white target was last shown. This was done using pygame and the pyjs package to convert to a javascript file. It should be a simple matter to find the Euclidian distance between the target and the participants' clicks if the mouse positions are recorded.

SpaDect_java (Pyjamas Auto-Generated HTML file)

Here is the code .