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
M.Duck
M.Duck is a roguelite gallery shooter about a duck that knows magic.
$1.99 · In-app purchases
PRICE
$1.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 4.8
75 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.
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 should your app do differently? Your note travels with the kit so your coding agent builds around your idea.
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 M.Duck: map the core Games 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 diverse game modes or challenges to keep gameplay fresh.
Assumption to check: Repetitive gameplay can lead to boredom.
Validate with people who use this workflow before building.
Hypothesis 2
Offer more ways to earn currency through challenges or daily tasks.
Assumption to check: Limited in-game currency options.
Validate with people who use this workflow before building.
Hypothesis 3
Implement multiplayer modes for competitive gameplay.
Assumption to check: Lack of multiplayer features.
Validate with people who use this workflow before building.
Hypothesis 4
Offer an ad-free experience through a one-time purchase or subscription.
Assumption to check: Ads can disrupt the flow of the game.
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
M.Duck is a roguelite gallery shooter about a duck that knows magic. Help Magic Duck fight his way up the mysterious tower that has been shining light on his pond each night and interrupting his sleep. Battle fearsome foes, discover new relics, uncover the secrets of the tower, and turn off that light once and for all! M.Duck combines roguelite features with gameplay inspired by classic gallery shooters to create a unique single-player experience. Features: - Battle over 40 different enemies and 8 unique bosses across 4 zones of the tower - Discover over 80 relics and 9 different weapons that promote a variety of different builds and playstyles - Waddle between offense and defense as you dodge attacks to find openings and blast enemies with your magic wand - Unlock additional lore, new relics, and even new game features as you fill out Magic Duck's field notes by climbing the tower and completing different challenges - Music composed by Calbert Warner
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
Supabase
React Navigation
React Native Reanimated
React Native Async Storage
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.
