Hi HN, I built Lentando, a privacy first tracker for substance use and habits (nicotine, alcohol, cannabis, or custom). It's an offline first PWA, no account required unless you opt into multi device sync. Released under GPL 3.0.

Under the hood it's about 6K lines of vanilla ES6 with no runtime dependencies. To make long term browser storage practical, it consolidates older events while keeping aggregates stable. Optional sync uses a simple conflict tolerant merge (event timestamps and tombstones) so offline edits across devices don't break. Charts are a small custom canvas renderer (stacked bar charts and heatmaps), and there's time travel debugging plus 100+ Node unit tests.

I'd love feedback from both developers and anyone who tries it, on the architecture, the UX, and what you would improve.

Repo: https://github.com/KilledByAPixel/Lentando Live: https://lentando.3d2k.com