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
Hafenskipper
Train to stop, dock and turn your ship with this realistic simulation app
$3.99 · In-app purchases
PRICE
$3.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 4.4
26 ratings · Top 30%
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.
Build your own version
Build Kit
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A product spec, screen plans, and build steps for your coding agent.
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What's included15 files
A product spec, phased build plan, differentiation notes, and screen references.
- START_HERE
- AGENTS
- EVIDENCE
- SPEC
- BUILD_PLAN
- DIFFERENTIATION
- skills/
- screens/
Preview a sample Build Kit No email needed
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 Hafenskipper: 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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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
Incorporate offline maps and harbor information.
Assumption to check: Limited offline functionality
Validate with people who use this workflow before building.
Hypothesis 2
Encourage and incentivize users to leave reviews.
Assumption to check: Not enough user reviews
Validate with people who use this workflow before building.
Hypothesis 3
Create a guided onboarding process for new users.
Assumption to check: Poor onboarding experience
Validate with people who use this workflow before building.
Hypothesis 4
Simplify the subscription model and clarify benefits.
Assumption to check: In-app purchase confusion
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
Train to stop, dock and turn your ship with this realistic simulation app. Maneuvering your ship in close quarters can be a challenge and must be trained well. Hafenskipper simulates harbor maneuvers under power and can help you to get a good understanding of the ship dynamics. Experienced users can work on specific maneuvers in the free running mode. Beginners can use the training levels to prepare for the next practical boating lessons. Your Mission: - Maneuver the ships safely through the harbor - Dock at the pier and park in the slip - Choose one of the 12 training levels or drive around freely - Complete one level successfully to unlock the next level Features: +Realistic physics simulation +6 ship types: Boat with outboard engine, motorboat, small dinghy boat, sailing yacht with engine, motor yacht with twin engine, catamaran +Motorboat and sailing yacht with prop walk +12 training levels +1 free running mode with optional wind and current simulation and mooring +1 free running bay mode with wind, mooring and anchoring Get Hafenskipper today!
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 Native
Expo
React Navigation
Axios
React Native Maps
Redux
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.
