Just a simple shape-drawing demo written in GW-BASIC, and rewritten in Python 3 and PyGame. It simply draws circles of a radius of 50 pixels, in 10-degree increments, 50px from the center of the screen, choosing a random color from the CGA 16-color palette. In the PyGame version, I've tried to annotate it as much as possbible, without making it unreadable.
The GW-BASIC version can be run in DOSBox in GW-BASIC, or in PC-BASIC, a fantastic interpreter written in Python 3. The Python version requires PyGame.
The bulk of the Python code comes from https://blubberquark.tumblr.com/post/185013752945/using-moderngl-for-post-processing-shaders-with