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
Math Facts Ninja - Math Games
Math Facts Ninja is a math game for kids (and adults) to improve basic math fact skills including Addition facts, Subtraction facts, Multiplication facts and Division facts
$0.99 · In-app purchases
PRICE
$0.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 3.9
154 ratings · Top 50%
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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Combine features and design from your favorite apps.
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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 included17 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 Math Facts Ninja - Math Games: map the core Education 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 game types and adjustable difficulty settings.
Assumption to check: Limited game variety and difficulty levels
Validate with people who use this workflow before building.
Hypothesis 2
Clearer explanations of what premium features include.
Assumption to check: In-app purchase confusion
Validate with people who use this workflow before building.
Hypothesis 3
Integrate social sharing and leaderboard features for competition.
Assumption to check: Lack of social features
Validate with people who use this workflow before building.
Hypothesis 4
Enable offline access to games and progress tracking.
Assumption to check: No offline functionality
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
Math Facts Ninja is a math game for kids (and adults) to improve basic math fact skills including Addition facts, Subtraction facts, Multiplication facts and Division facts. Looking for multiplication games to make learning math facts more fun then simple multiplication flash cards? Not your standard math flash cards game, Math Facts Ninja uses three math games to test your "ninja-like-skills" as you try to earn your black belt in each ninja skill. These skills include Sword, Throwing Stars and Hands. As you progress though the eight belt levels of each skill you are challenged with increasingly difficult math problems designed to improve your mastery of Math Facts in addition, subtraction, multiplication and division (+-x÷). Features in Math Games: • Math Facts, Math Drills and Math Games • Common Core 3.OA.C.7 • Operations & Algebraic Thinking • Multiply and divide within 100 • STEM math basics • More Fun than Math Facts Flash Cards • Learn & Practice Times Tables Game • Learn & Practice Addition Game • Learn & Practice Subtraction Game • Learn & Practice Division Game • Math Facts Dojo to practice your math fluency • Fun ninja math facts games and math drills • Way more fun then simple math flash cards Math Facts Dojo: In the Math Facts Ninja Dojo (practice room), you can practice specific number sets and arithmetic operations. Hone your skills as you focus on the areas you want to improve upon. You get to decide the Math Game and the Number Set as well as the number of math questions you want. Practicing your times tables has never been so much fun! Math Facts Ninja is the perfect study app for students in grades 3 to 6, or anyone wanting to improve their general math facts skills. Math Facts Ninja offers multiple levels of difficulty, represented as belt levels, in a fun game environment. The more you play the more your math facts fluency will improve. Math Facts Ninja helps improve your math fluency in a fun, self—paced, game environment. Three different ninja-like games offer eight stages of difficulty culminating in the ultimate prize, a Black Belt! Earn a black belt for each ninja skill.
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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
AsyncStorage
Redux
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.
