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
Wa Kingyo - Goldfish Pond
Goldfishes drawn on the Japanese style of painting swim elegantly
$1.49 · In-app purchases
PRICE
$1.49
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 4.7
529 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 included18 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 Wa Kingyo - Goldfish Pond: map the core Entertainment 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
Introduce more activities and customization for goldfish.
Assumption to check: Limited interaction options for users.
Validate with people who use this workflow before building.
Hypothesis 2
Offer a free trial period or demo features.
Assumption to check: In-app purchases may deter some users.
Validate with people who use this workflow before building.
Hypothesis 3
Add seasonal events or challenges to engage users.
Assumption to check: Repetitive gameplay can lead to boredom.
Validate with people who use this workflow before building.
Hypothesis 4
Implement a sharing or competitive aspect with friends.
Assumption to check: Lack of social features.
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
Goldfishes drawn on the Japanese style of painting swim elegantly. You will be surprised at their cute movement and the clear water. Please scatter the flower-shaped bait. And enjoy a relaxing time. ************************************************** Introduced as "What's Hot" in 64 countries. Jan 2020 - No.1 Top Paid App in Japan. ************************************************** Video on YouTube: http://www.youtube.com/watch?v=4Gru8myVzQA (Please search with these words "Wa Kingyo" on YouTube.) Actions: - touching the goldfish - scattering bait that looks like flowers and leaves (please tap the lower right-hand corner to begin) - getting rid of the bait by tilting the iPhone - touching the water to make it ripple - making waves by shaking the iPhone Customize: - Background (11 images) - Bait (5 types) - Number of goldfish (up to 4) - Color of goldfish (4 colors, 10 combinations) - Size of goldfish - Sleep timer (5-60 minutes) - Sound volume Theme: "Wa" has several means "Peace", "Relaxation" and "Japan". And "Kingyo" means "Goldfish". The theme of this application is beauty and prettiness of the Japanese traditional classic art. The goldfish and background images are drawn like a Japanese traditional painting and industrial art object. The bait has a shape of the familiar flower and leaf (cherry blossom, chrysanthemum, camellia, myosotis, maple) for Japanese. Please feel Japanese mind. News & Support: @m_hakozaki on Twitter
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
Redux
axios
react-navigation
expo-animated
BUILD KIT DIFFICULTY
Intermediate
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.
