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
Stair Tangent
Professional Stair Builders don't need an app to build stairs, they just know how to build stairs
$7.99 · In-app purchases
PRICE
$7.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 2.3
3 ratings · Below Average
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'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 Stair Tangent: map the core Business 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
Ensure thorough testing and debugging before release.
Assumption to check: Limited user reviews indicate poor performance or bugs.
Validate with people who use this workflow before building.
Hypothesis 2
Offer more value with additional features or free trial.
Assumption to check: The app has a high price point with limited features.
Validate with people who use this workflow before building.
Hypothesis 3
Implement better onboarding and user guidance.
Assumption to check: User interface may be confusing for new users.
Validate with people who use this workflow before building.
Hypothesis 4
Introduce user preferences for calculation methods and units.
Assumption to check: Lack of customization options for calculations.
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
Professional Stair Builders don't need an app to build stairs, they just know how to build stairs. This iPhone app is for rough frame carpenters that don't build stairs everyday, but could use an stair building app calculator to check their stair building calculations. Build a set of stairs that you are gonna be proud of. With Stair Tangent you can elimenate cumulative math errors when building - constructing stairs. Six different types of stairs Build Stairs with: Locked Tread Width Unlocked Tread Width 45 Degree Stair Stringers Flared Stair Stringers Circular Stairs Stair Landing Height Enter a couple of dimensions to see all of the information you need to build your stairs. Layout circular stairs in 10 minutes or less. Stair Riser Height and Stair Tread Width Building Code Complaint Error checking for Minimum stair Riser height of 4 1/2". Error checking for Maximum stair Riser height of 7 3/4". Error checking for Minimum Stair Tread Width of 10". Error checking for Circular Stairs with Minimum Stair Inside Tread width of 8". Error checking for Circular Stairs with Minimum Stair Walk Line Tread width of 10".
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
Zustand
react-native-paper
react-native-share
expo-router
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.
