Hitherto, like probably most people, I had been viewing source code in the same programs in which I wrote it (mostly Notepad++ or VS Code). Decided reading code is an important enough use case to justify a dedicated program to do it better.

Also a test case for Claude Code. It performed well. Caveat: there are some dimensions of difficulty this project did not exercise. In particular, good performance writing a small program from scratch, doesn't guarantee anything about how well it will do on a large existing code base.