I run a granite-slab yard and I’m ready to replace my paper logbook with a small Android app that lets me capture slab sizes, apply dealer allowances, total everything lot-wise, and issue a tidy PDF invoice that I can save to the phone and forward on WhatsApp. Core workflow • Screen one lets me enter each slab’s length and width in inches, select how many pieces, and instantly see the net square footage after I pick an allowance—3", 6", 9" or 12". • Every entry belongs to a lot number; at any time I can open a lot and view its running total sqft. • When it’s time to bill, I choose the lot, add or deduct extra charges or discounts as needed, and generate a simple invoice. A single tap saves the PDF locally and opens the WhatsApp share sheet for quick sending. Technical notes The build can be in clean Flutter or fully native Android—whichever lets you deliver an uncluttered UI, offline-first data storage, and smooth PDF generation. All calculations must work without a network connection; syncing can wait for a later phase. Timeline & hand-off I’d like the first APK within 20–25 days. When we wrap up, I’ll need: • Signed APK ready for install • Entire source code with clear comments • Up to 15 days of bug fixes after delivery If this sounds achievable in your stack, let’s get started.