Thanks a lot, this is really useful feedback! You're right that the preset shapes (especially the spiral) aren't perfectly even yet — I'm going to add proper parametric shape generators (spiral, oval, rounded-rect, etc.) with evenly-spaced cells, which should fix the "amateur" look you mentioned. More board shapes are definitely on the roadmap.
Quick note on the offline part: it actually already works fully offline — it's a standalone HTML file, so you can download the zip and just open index.html with no internet. I'll make that clearer on the page. A packaged desktop version is something I can look into too.
Really appreciate you taking the time to test it properly