Minify the the admin configuration page a bit more.

These styles help compress the configuration page to better mimic what I wanted to achieve originally.
Group the radio options in a common div.

This helps target them specifically with CSS.
Removal of several unnecessary resources from the original captcha library.

There were several dictionaries and other resources in the original captcha library that aren't needed in Core.
Rewrite of the logic behind the simplecaptcha system.

Since the original maintainer is not really maintaining this library, I felt it safe to rewrite the application under Core coding guidelines.
Captcha is fully configurable via an admin interface.

The captcha is (nearly), fully configurable via an admin page.
The only elements currently not manageable are the foreground and background colors.  These could make use of the jquery color picker.