Ciro Santilli's favorite. A mixture of painting and book.

There is just one key gotcha: the project has to be useful.

The set of all invertible matrices forms a group: the general linear group with matrix multiplication. Non-invertible matrices don't form a group due to the lack of inverse.

See: eigenvalues and eigenvectors.

PNG reference implementation. Ahh, if feels good to have a dominating open source reference implementation.

Demo of using it by Ciro Santilli: stackoverflow.com/questions/1362945/how-to-decode-a-png-image-to-raw-bytes-from-c-code-with-libpng/36399711#36399711

Default mathematics typesetting used in OurBigBook Markup.

Key issues:

CommonMark is a good project. But its initial release method was not very nice, they first developed everything behind closed doors with the big adopters like GitHub and Stack Overflow, and only later released the thing read, thus wasting the time of people who were working on alternative in the meanwhile, e.g. github.com/karlcow/markdown-testsuite which Ciro contributed to: Ciro Santilli's minor projects.

Ciro Santilli's joke version of the Chinese Four Treasures of the Study!In the past, Ciro used to use file managers, which would be the fourth tresure. But he stopped doing so for years due to his cd alias... so it became three. He actually had exactly three windows open when he was checking if there was anything else he could not open hand of.