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
Terrafin Mobile
Terrafin has provided key satellite data online for anglers, divers, and researchers since 1998
Free · In-app purchases
PRICE
Free
In-app purchases
BUSINESS MODEL
Freemium
No overall Grossing estimate available
RATING
★ 5.0
1 ratings · Top 5%
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 included16 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 Terrafin Mobile: map the core Weather 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
Implement a more reliable weather API with comprehensive data.
Assumption to check: Limited weather data accuracy and coverage
Validate with people who use this workflow before building.
Hypothesis 2
Create a cleaner layout focusing on user-friendly data presentation.
Assumption to check: Cluttered user interface with too much information
Validate with people who use this workflow before building.
Hypothesis 3
Optimize data fetching and caching strategies to improve load times.
Assumption to check: Inconsistent loading times for radar data
Validate with people who use this workflow before building.
Hypothesis 4
Allow users to customize alert settings based on their preferences.
Assumption to check: Lack of personalization in alerts
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
Terrafin has provided key satellite data online for anglers, divers, and researchers since 1998. Now, Terrafin Mobile gives subscribers easy access to this data from your iPhone or iPad. Note: The Terrafin Mobile app installs with an assortment of sample charts, that you can use to try the various features. Access to current data requires an active subscription to the Terrafin website, available @ $119/year. Terrafin Mobile Features: • Browse Terrafin website to easily select charts. • Charts are downloaded to device for use offline. • Tap and drag cursor for accurate positioning. • Latitude / Longitude / Temperature readings at cursor. • Mark waypoints. • Distance & Bearing to waypoint or cursor. • Real time vessel location and track displayed on chart (GPS enabled device required). Data available with Terrafin Mobile • Hi Res (1.1km) Sea Surface Temperature Charts, updated multiple times daily. • Hi Res (1.1km) Chlorophyll / Ocean Color Charts, updated daily. • Altimetry (Sea Surface Height) Charts, updated daily. • Geostrophic Currents Charts, updated daily. • CloudFree SST charts, updated daily. • LEO 1 Day Composite SST charts, updated daily. Areas of Coverage: • U.S. East, West, and Gulf Coasts • Alaska & Hawaii • Caribbean & Bermuda • Mexico, including Baja and Sea of Cortez • Central America (Pacific Coast) • Venezuela • Brazil • Australia East Coast • Northwest Africa SAVE FUEL – SAVE $$$ - CATCH MORE FISH!
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.
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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.
