Feature spec
Goal: Send a clear invoice after finishing a job.
- Add a client, line items, a due date, and payment instructions.
- Preview the total before exporting a PDF.
- Keep an editable draft if export fails.
You worked out the price at the hardware store
$1.99 · In-app purchases
Evidence scope: No current overall US chart position is available. Category-chart positions shown in discovery are a separate scope. Revenue is a directional model estimate, not verified earnings.
A product spec, screen plans, and build steps for your coding agent.
First kit free with a verified email
Combine features and design from your favorite apps.
Your first Build Kit is free with a verified email.
Generating… usually about a minute.
What should your app do differently? Your note travels with the kit so your coding agent builds around your idea.
A product spec, phased build plan, differentiation notes, and screen references.
Illustrative example: an invoice app for independent contractors. Your kit is tailored to the app you choose; this is not its generated content.
Goal: Send a clear invoice after finishing a job.
Invoice editor: Client at the top, editable line items in the middle, total and preview action at the bottom.
States: Empty draft, validation errors beside each field, exporting, and a retry action that preserves the draft.
Hypothesis: Contractors need faster repeat invoices more than more templates.
First experiment: Test duplicating a previous job with five contractors. Watch where they hesitate before expanding the feature set.
The full kit adds a phased build plan, evidence notes, tool prompts, and implementation guidance. It is a plan for your coding agent, not a finished app.
Usage: Mechanics are fair game; never reuse the original name, branding, assets, or verbatim copy.
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Good fit for mobile-first iOS and Android prototypes with managed app scaffolding.
Rork plan preview for Sumwhere Calculator: map the core Productivity workflow, choose the smallest differentiated feature set, define the data and monetization boundaries, then prototype the riskiest user journey first.
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Original App Store material. Ratings and screenshots describe the existing app, not proof of demand for your version.
You worked out the price at the hardware store. A week later you're ready to start that project and it's gone. Sumwhere keeps every result you calculate, along with when and where you worked it out. It looks and works exactly like the calculator already on your phone. The difference is what happens after you total it up. Every result is quietly saved with the date, weekday, and time of day. Turn on location and it'll also remember where you were standing, so a number you worked out at the hardware store on a Monday morning or a customer's house on a Thursday afternoon is easy to find again, even weeks later. All the muscle-memory details of the calculator you already use. Switch to the scientific keypad, and landscape expands it into a familiar wide grid. For those who hate science but still like to remember — memory keys (MC, M+, M-, MR) sit on both keypads, with a clear on-screen indicator showing what they're currently totalling. Search your history by the numbers, by a date range, weekday, time of day, or by place, with an adjustable radius for when you can't remember exactly where you were. Add tags and notes, pin favorites, and browse everything in a clean, organized list. It turns your calculator into an actual record of your math. You won't brag about it to your friends, but you'll find it incredibly useful when you need it most. Location, entirely on your terms Location stamping is off by default. Turn it on only if you want it, and everything stays on your device - nothing is uploaded, no account required, no tracking, no analytics. Apple's own privacy label says it plainly: Data Not Collected. Made to be customized Eight accent colors, a choice of standard or scientific as your default keypad, adjustable history retention. No subscriptions. No in-app purchases. No ads. Just a calculator that remembers the sum and the somewhere. How much time would you save if you had better access to the math you've already done? Oh, you've already done the math? Good luck remembering it in a week. Download Sumwhere.
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These are generated suggestions, not verified review quotations. Check current App Store reviews and speak with users before treating a possible gap as a requirement.
Hypothesis 1
Assumption to check: No offline mode
Validate with people who use this workflow before building.
Hypothesis 2
Assumption to check: Sync issues
Validate with people who use this workflow before building.
Hypothesis 3
Assumption to check: Feature bloat
Validate with people who use this workflow before building.
Plan a focused first version with your coding agent. These are planning assumptions, not a delivery guarantee.
Choose one audience and one core workflow. Use the kit to agree on its screens, data, and acceptance criteria before building.
Decide which secondary features, integrations, and platform support can wait. Your version does not need to reproduce everything in the original.
Validate external services, specialist technology, data access, and ongoing costs for your chosen scope.
Not assessed in a Build Kit yet.
A reliable timeline needs an agreed scope and a technical check. Ask your agent to estimate the phases in BUILD_PLAN.md after that review.