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.
grains is a simple archery calculator that makes it convenient to calculate a few important numbers like total weight, foc (front of center), speed, and energy.
$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.
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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 Grains: Archery Calculator: map the core Sports workflow, choose the smallest differentiated feature set, define the data and monetization boundaries, then prototype the riskiest user journey first.
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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: Limited features compared to more comprehensive sports calculators
Validate with people who use this workflow before building.
Hypothesis 2
Assumption to check: User interface feels basic and outdated
Validate with people who use this workflow before building.
Hypothesis 3
Assumption to check: In-app purchases are not clearly communicated
Validate with people who use this workflow before building.
Hypothesis 4
Assumption to check: Lack of user community or sharing options
Validate with people who use this workflow before building.
Original App Store material. Ratings and screenshots describe the existing app, not proof of demand for your version.
grains is a simple archery calculator that makes it convenient to calculate a few important numbers like total weight, foc (front of center), speed, and energy. total weight: when building an arrow, you're working with many small components with various weights. grains helps you keep track of each component's weight and see your total arrow weight and how individual components will affect it. foc: your arrow build's front of center percentage is an important factor when it comes to building an accurate hunting arrow. it's a relatively simple calculation to do, but grains makes it even easier, even offering some advice for an ideal setup and the how-to of getting an accurate measurement. speed: arrow speed is another factor that's important in building the perfect arrow. the slower the arrow, the more likely you are to experience game "jumping the string." grains uses a standard formula to calculate an estimate of how your bow setup and arrow build might be performing. energy: a fast arrow with good foc is only good if it carries enough energy. arrow weight and speed can give you the total energy that your arrow will carry, and grains will also show you what game your arrow build works for.
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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.
From the Build Kit assessment.
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.