Today every second website affected spammer bots that can reads graphics data from pattern image and automatically send post data. There are many completed solutions and services fro secure a websites but I steel create own Captcha.
This encryption simple and fast. It's not to brake client and does not provide the possibility of bulkheads. With RevolveR CMS not dependencies needed to use RevolveR Captcha. It was integrated in core.
Maybe later, when I have to create fully randomized patterns I may to create a new Captcha service that more user-friendly end fast than Google services to allow other CMS users use this Captcha.