Colosseum

A (partial) implementation of the CSS box and flexbox layout algorithm.

Toga

A Python native, OS native GUI toolkit.

Ouroboros

A standalone, pure Python implementation of the Python Standard Library. This allows Python default libraries to be used portably on any implementation of the Python virtual machine---not requiring CPython.

Libraries are re-usable blocks of code that can be used in a project. Libraries will usually be installed as dependencies of tools, applications, or other libraries.