PySol

Pysol is a free, open-source, solitaire game written in Python. While the initial release only had four types of solitaire included, the engine is extensible; the final version contains over 200. It supports unlimited undo/redo, has sound and animation, multiple deck types, and has rules, hints, and a demo mode to assist in learning the solitaire variants.

In 2004, the main author stopped developing it, with PySol Fan Club Edition eventually taking over.