I like baking sourdough bread, so I always have sourdough starter around. And it turns out you can replace instant yeast in flour-based recipes with sourdough starter.
I found a formula online for converting an instant-yeast recipe to use sourdough starter, and at first I was just doing the math manually. Then I made a spreadsheet to do the math for me.
Then I realized I'm usually on my phone or tablet when cooking, so why not make a tiny little web app for it? It was also a good excuse to try out a little personal design system I was working on.© Chad Lavimoniere