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
Kotomaji: Japan Phrases
Planning a trip to Japan? Kotomaji is your essential companion to communicate confidently on your Japanese adventure.
$2.99 · In-app purchases
PRICE
$2.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
N/A
No ratings yet
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 should your app do differently? Your note travels with the kit so your coding agent builds around your idea.
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 Kotomaji: Japan Phrases: map the core Travel 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 gamification elements and daily phrases to keep users engaged.
Assumption to check: Limited phrase variety and context may lead to user boredom.
Validate with people who use this workflow before building.
Hypothesis 2
Add user profiles with progress tracking and personalized phrase recommendations.
Assumption to check: No personalized learning paths or progress tracking.
Validate with people who use this workflow before building.
Hypothesis 3
Implement forums or chat features for users to practice with each other.
Assumption to check: Lack of community or social interaction features.
Validate with people who use this workflow before building.
Hypothesis 4
Enable offline mode for accessing favorite phrases without internet.
Assumption to check: No offline access to phrases.
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
Planning a trip to Japan? Kotomaji is your essential companion to communicate confidently on your Japanese adventure. ESSENTIAL TRAVEL PHRASES 222 carefully selected phrases for real situations you'll encounter in Japan: - Greetings and Japanese etiquette - Restaurants and food - Transportation (train, taxi, subway) - Hotels and accommodations - Shopping and bargaining - Directions and navigation - Medical emergencies - Numbers and prices - Culture and respect - Useful everyday phrases FREE: 155 essential phrases included PRO: 67 additional premium phrases OUTSTANDING FEATURES REAL AND NATURAL AUDIO - Over 570 professional audio recordings - Male and female native speaker voices - Normal and slow speed for practice - Perfect pronunciation with ElevenLabs COMPLETE JLPT KANJI - 1,097 kanji characters (N5 to N1) - Meanings in Spanish and English - Onyomi and kunyomi readings - Usage examples in context - Animated stroke order - Favorites system for study INTEGRATED CURRENCY CONVERTER - Real-time JPY conversion to 14 currencies - USD, EUR, GBP, AUD, CAD, MXN, BRL, KRW, THB, and more - No additional app needed - Automatic rate updates BEAUTIFUL AND FUNCTIONAL DESIGN - Modern SwiftUI interface - Full dark mode - Shareable cards with QR code - Smooth animations and micro-interactions - Pull-to-refresh in all views INTERACTIVE PHRASES WITH NUMBERS - 9 phrases with customizable numbers - "Table for X people" (1-10) - "X tickets please" (1-6) - "That's X yen" (100-10,000) - Dynamic audio for each variant PREMIUM USER EXPERIENCE - Mark favorites for quick access - Instant multilingual search - Organization by categories - Interface in Spanish and English - Works 100% offline - No ads or distractions - Your privacy comes first FAIR FREEMIUM MODEL Kotomaji offers a transparent business model: FREE VERSION - 155 essential phrases (~70%) forever - 104 complete N5 kanji - All audio features available - Unlimited currency converter UPGRADE TO PRO (one-time purchase) - 67 additional premium phrases - 993 complete JLPT kanji N4-N1 - Lifetime access - No subscriptions or recurring charges - Buy once, enjoy forever PERFECT FOR - Travelers visiting Japan for the first time - Japanese learners (beginner to advanced) - Anime and manga fans - Tourists who want to communicate better - Business travelers - Anyone interested in Japanese culture WHY KOTOMAJI Unlike other language apps, Kotomaji was designed specifically for real travelers. You won't find endless theoretical lessons here, but practical phrases you'll actually use. Each phrase was selected based on common situations tourists face in Japan. Professional audio gives you confidence when speaking, and slow pronunciation helps you learn. The integrated currency converter means one less app to install. JLPT kanji allow you to continue your learning beyond the trip. Your adventure in Japan starts here. Download Kotomaji and start speaking Japanese today. Gute Reise! (Have a good trip!) --- Developed by Quantum Quacks
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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
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expo-image
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.
