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
Krux - Markdown Editor
You open a long markdown document on your iPhone
$4.99
PRICE
$4.99
No in-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 5.0
1 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.
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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 included
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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Quick prompt
Good fit for mobile-first iOS and Android prototypes with managed app scaffolding.
// RORK SYSTEM PROMPT
Rork plan preview for Krux - Markdown Editor: map the core Productivity workflow, choose the smallest differentiated feature set, define the data and monetization boundaries, then prototype the riskiest user journey first.
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App evidence
Original App Store material. Ratings and screenshots describe the existing app, not proof of demand for your version.
Screenshots
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App Store description
You open a long markdown document on your iPhone. You need section four. You scroll. And scroll. And scroll. Your current editor -- the one that costs $19.99, or charges you every month -- doesn't have a document outline on iPhone. It never has. You've been asking for years. Krux has it. Day one. Tap the outline panel and jump to any heading in your document instantly. On iPhone. On iPad. On Mac. It works the way it should have always worked. --- WRITE EVERYWHERE Krux is a native markdown editor built for every Apple device you own. iPhone, iPad, Mac, Apple Watch. Your documents sync through iCloud Drive as standard .md files -- the same files you open in VS Code, BBEdit, or any editor you choose. Dictate a note on your Apple Watch while your phone is in your bag. It's in your Files app by the time you sit down. --- WHAT YOU GET -- Document outline with jump-to-heading navigation on every platform -- Live syntax highlighting with real-time preview -- Side-by-side preview on iPad and Mac, tabbed preview on iPhone -- Focus mode that dims everything but the current paragraph -- Apple Watch companion with dictation, offline reading, and watch face complication -- Export to HTML, PDF, or raw markdown in one tap -- Formatting toolbar with 13 actions plus full keyboard shortcuts -- OLED-optimized pure-black dark mode -- iOS 26 Liquid Glass design, built in Swift --- YOUR FILES. YOUR FORMAT. FOREVER. Every file Krux creates is a plain .md file. No proprietary database. No invisible metadata. No lock-in. Open a Krux file in any other editor -- it looks exactly the same. Because it is exactly the same. Standard markdown, stored in your iCloud Drive, readable everywhere. Zero data collection. No accounts. No tracking. Confirmed by Apple's required PrivacyInfo.xcprivacy declaration. --- ONE PRICE. NO SUBSCRIPTION. Pay once. Write forever. No monthly fee. No annual renewal. No "upgrade to Pro." Krux for iPhone and iPad: $4.99. Krux for Mac: $9.99. Apple Watch companion: included. --- THE LANGUAGE OF AI, NATIVELY Claude Code, ChatGPT, and GitHub Copilot all write in markdown. Krux is where that output lives on your iPhone -- rendered cleanly, navigated with the outline, stored as plain files that feed right back into your workflow. Markdown is the language of AI. Krux is its native home. --- Built for iOS 26 with Liquid Glass. Runs on iPhone and iPad. ---
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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
Implement a more robust rendering engine for accurate previews
Assumption to check: Markdown preview may not render accurately for all elements
Validate with people who use this workflow before building.
Hypothesis 2
Add more advanced markdown features like tables and footnotes
Assumption to check: Limited formatting options compared to other editors
Validate with people who use this workflow before building.
Hypothesis 3
Introduce collaboration tools for multiple users to edit documents simultaneously
Assumption to check: No collaborative features for real-time editing
Validate with people who use this workflow before building.
Hypothesis 4
Allow users to import and export documents in various formats (Markdown, HTML, etc.)
Assumption to check: No support for importing/exporting documents
Validate with people who use this workflow before building.
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
Zustand
react-native-webview
expo-file-system
@react-navigation/native
BUILD KIT DIFFICULTY
Not assessed in a Build Kit yet.
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.
