Test Advanced Image-Based Bot Detector
This is a variant of the image-based bot detector that uses unique nonrecurring template background image.
The image is fetched from Google's image search results in a random way.
This approach allows to set theme of template images by means of fitted seach keywords.
Also it makes impossible a manual recreation of images set - because there is no any images set!
This is "very" beta version.
Click on the distorted part of the image
Here is implementation (code).