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.
App Overview
Nautical Charts & Maps
Main Features Include:
$8.99 · In-app purchases
PRICE
$8.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 4.6
3,791 ratings · Top 15%
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.
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Build Kit
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A product spec, screen plans, and build steps for your coding agent.
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What's included17 files
A product spec, phased build plan, differentiation notes, and screen references.
- START_HERE
- AGENTS
- EVIDENCE
- SPEC
- BUILD_PLAN
- DIFFERENTIATION
- skills/
- screens/
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Illustrative example: an invoice app for independent contractors. Your kit is tailored to the app you choose; this is not its generated content.
Screen plan
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.
Differentiate and validate
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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Free quick prompt For a smaller starting point
Quick prompt
Good fit for mobile-first iOS and Android prototypes with managed app scaffolding.
// RORK SYSTEM PROMPT
Rork plan preview for Nautical Charts & Maps: map the core Navigation workflow, choose the smallest differentiated feature set, define the data and monetization boundaries, then prototype the riskiest user journey first.
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Opportunities
AI-GENERATED OPPORTUNITY HYPOTHESES
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
Offer more robust offline map features and caching.
Assumption to check: Limited offline functionality
Validate with people who use this workflow before building.
Hypothesis 2
Introduce lower-tier pricing or ad-supported options.
Assumption to check: High subscription cost
Validate with people who use this workflow before building.
Hypothesis 3
Simplify the UI for easier navigation and access to key features.
Assumption to check: User interface complexity
Validate with people who use this workflow before building.
Hypothesis 4
Ensure regular updates of nautical charts and user-reported issues.
Assumption to check: Inconsistent map updates
Validate with people who use this workflow before building.
App evidence
Original App Store material. Ratings and screenshots describe the existing app, not proof of demand for your version.
App Store description
Main Features Include: + NOAA Electronic Navigational Charts (ENC) + NOAA Weather Map Overlays -- ELECTRONIC NAVIGATION CHARTS -- Electronic Navigational Charts (ENC) are vector data sets that support all types of marine navigation. + All charts are available to download for offline use + Chart format options include: NOAA, ECDIS ENC charts display the following information: + Buoys, Beacons, Lights, Fog Signals, Radar + Natural and Man-Made Features + Services and Small Craft Facilities + Seabed, Obstructions, Pipelines + Depths, Currents + Port Features + Traffic Routes + Special areas NOAA updates the ENCs for Notice to Mariners on a weekly basis. Timing of their availability is not guaranteed. The ENC charts displayed in this app does NOT meet federal chart carriage regulations for regulated vessels. Users should consult the Code of Federal Regulations for current federal chart carriage requirements. -- NOAA WEATHER MAP OVERLAYS -- + Weather Radar + Sea Surface Temperature + Significant Wave Height + Wind Speed & Direction + 12-Hour Rain Probability + Lightning Strike Density + Air Temperature If you have any questions, please email [email protected]
Written user reviews are not shown here. Check current App Store reviews >
Screenshots
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Build scope
Plan a focused first version with your coding agent. These are planning assumptions, not a delivery guarantee.
Define the first version
Choose one audience and one core workflow. Use the kit to agree on its screens, data, and acceptance criteria before building.
Set boundaries
Decide which secondary features, integrations, and platform support can wait. Your version does not need to reproduce everything in the original.
Check the hard parts
Validate external services, specialist technology, data access, and ongoing costs for your chosen scope.
SUGGESTED BUILD STACK
React Navigation
React Native Maps
Axios
Zustand
Expo Location
Shadcn/ui
BUILD KIT DIFFICULTY
Advanced
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.
