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
Slider Calc
Slider Calc Mortgage Calculator is not your typical, boring mortgage calculator..
$1.99 · In-app purchases
PRICE
$1.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 4.2
5 ratings · Top 30%
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 included14 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 Slider Calc: map the core Finance workflow, choose the smallest differentiated feature set, define the data and monetization boundaries, then prototype the riskiest user journey first.
Preview ready. Verify your email to reveal and copy the full prompt.
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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 better history tracking and calculation saving.
Assumption to check: Limited calculation history management
Validate with people who use this workflow before building.
Hypothesis 2
Expand settings for custom user preferences.
Assumption to check: Lack of detailed settings options
Validate with people who use this workflow before building.
Hypothesis 3
Introduce subscription for ongoing features or updates.
Assumption to check: Single payment option without subscription
Validate with people who use this workflow before building.
Hypothesis 4
Add real-time feedback for more engaging user experience.
Assumption to check: No real-time value feedback while adjusting sliders
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
Slider Calc Mortgage Calculator is not your typical, boring mortgage calculator... SliderCalc is a unique, creative financial tool designed for anyone who likes to "slide" numbers around and create "what-if" scenarios when calculating mortgage payments and loan amounts. Home buyers , real estate professionals and investors will appreciate this slick re-invention of the typical mortgage calculator as you now literally slide the numbers around. Key Features: • Easy to grab interactive sliders let you set and change interest rates, monthly payment amount or loan amount. And they automatically re-center so you can slide to any value, not just a preset range of values. • Watch App is easy to use with a simple tap and dial. Slidercalc for WatchOS was designed for usability, and is aiming to be the best mortgage calculator for Apple Watch! • Lightning Fast! Calculations that update as soon as you make a change. • Automatically switches between calculating loan amount or monthly mortgage payment depending on what is being modified. No need for multiple screens or controls. • Optional keyboard entry for precision when you need to calculate to the nearest $.01 or 1/1000th of a percent. • Calculations for fixed-rate mortgages of any term. From the most popular 30-year & 15-year loans to the more unusual 10-year, 40-year or any number of years you enter. You'll get quick answers to your loan financing questions because SliderCalc isn't bogged down with details like PMI, property taxes, insurance, down payments and closing costs. It is the perfect tool to calculate mortgage interest rates, payments, and loan amounts with the freedom to "slide" those numbers around and test alternative scenarios. - July 22, 2010 *iOS4 Users: You will be happy to find that the bug in the % rate display has been fixed in this release. Thanks to everyone for their feedback!
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 Navigation
@react-native-community/slider
react-native-async-storage
BUILD KIT DIFFICULTY
Starter
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.
