Lentic is a package which implements lenticular text — two Emacs buffers that contain the same content, but are otherwise independent. Unlike indirect-buffers, which must contain absolutely identical strings, lentic buffers can contain different text, with a transformation between the two.
It was not my original plan to have another release so soon after the last release (n.d.) However, the work that I had planned for that release turned out to be very-straightforward.
For this release, introduces a new form of buffer which is an unmatched block buffer. The details do not matter — the practical upshot is that with, for example, org-mode it is now possible to have more than one style of source block. In my examples directory, I have an org-mode file with "hello world" in three different languages (Clojure, Python and Emacs-Lisp). When lentic, you get four views, each in a different mode, and syntactically correct. Not a use I think I would suggest, but a nice demonstration.