* https://repo.autonoma.ca/repo/treetrek/tree/HEAD/render/rule... - syntax highlighting for 40 languages and file formats in ~10 minutes
* https://shufflenblues.com/expenses/ - real-time expenses progress updates with payment vendor API in ~30 minutes
* https://repo.autonoma.ca/repo/treetrek/tree/HEAD/git - real-time, cache-free raw Git reader implementation with cloning in ~5 days
* https://repo.autonoma.ca/repo/notanexus - PDFjs integration in ~3 days
However, these are likely not the "hard" problems you've mentioned. I feel like I can architect solutions at a higher-level now, without having to be completely caught up in many technical nuances. I'd rather not learn the extensive PDFjs API, for example, because it would take weeks of effort to understand.