As I planned, version 2.4.1 introduces unit tests to the project. They can be run from the page UnitTests.html. The unit tests did help me ferret out a few bugs and help me verify that exponentiation of complex numbers was being done correctly.
The major new feature of this version is that you can now raise a complex number to a complex argument, expanding the number of fractals you can draw!
Version 2.4.0 fixed a bug where images were being drawn upside down. This was a big deal because some fractals, such as the "Burning Ships", are almost always presented upside down, so it took quite a bit of work before I realized what was going on. I fixed this bug in the process of fixing the bug where wrong numbers were being displayed for the imaginary coordinates in the complex plane.
The 2.3 versions introduced some minor improvements; I did a major code-cleanup using Douglas Crockford's JSLint. I also used some immature cross-browser compatibility code than I worked on with Cameron Henlin in GitHub. This code allows the touch programming to work in MS IE, but as before, I never use that browser because it runs my Javascript so slowly. I learnt that IE uses "Pointer Events", which are completely different from the W3C standardized "Touch Events", so touch programs have to be written either for the W3C standard or the IE way. Hopefully, as this cross-compatibility library matures, the choice will become irrelevant.