Knitters and crocheters constantly face the same frustration: they find a gorgeous pattern that calls for 400 yards of worsted weight yarn, but their stash skeins only show weight in grams. Build a single-page widget that helps crafters instantly convert between yarn weight (grams) and yardage based on yarn thickness category.

The app should let a user:
1. Enter how many grams of yarn they have
2. Select a yarn weight category from a dropdown (Lace, Fingering, Sport, DK, Worsted, Bulky, Super Bulky) — each category has a known average yards-per-gram ratio
3. See the estimated total yardage instantly
4. Optionally enter a pattern's required yardage and see whether their stash is enough, with a clear yes/no indicator and how many grams short or surplus they are

The UI should feel warm and crafty — think soft colors, maybe a small yarn ball icon. All math happens client-side with no backend needed. Keep the layout clean enough that a crafter can use it on a phone while standing in a yarn shop.