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
Gas Oil Mixture Ratio
The Gas Oil Mixture Ratio app automatically calculates the quantity of oil required for a given ratio of fuel and oil
$0.99 · In-app purchases
PRICE
$0.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 5.0
4 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 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 Gas Oil Mixture Ratio: 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
Add features like saving favorite ratios and sharing calculations.
Assumption to check: Limited functionality beyond simple calculations
Validate with people who use this workflow before building.
Hypothesis 2
Incorporate user feedback and a rating system for ratios.
Assumption to check: Lack of user engagement features
Validate with people who use this workflow before building.
Hypothesis 3
Implement localization for broader accessibility.
Assumption to check: No support for multiple languages
Validate with people who use this workflow before building.
Hypothesis 4
Enhance UI/UX with modern design principles and animations.
Assumption to check: Basic design and UX
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
The Gas Oil Mixture Ratio app automatically calculates the quantity of oil required for a given ratio of fuel and oil. No ads. No subscriptions. Network connection not required to use. This app works great for engines used for recreational and transportation, such as commercial two-cycle carts, golf carts, rotary plows, snowmobiles, blowers, chainsaws, tillers, utility tractors, garden tools, motorcycles, motor scooters, motor skates and other two cycle engines. Also included are unit converters for area, distance, volume, and temperature. Calculators: 1. Gas/Oil Mixture (US Units/Metric) 2. Petrol/Oil Mixture (Imperial Units/Metric) 3. Raw Gauge Value Calculator 4. Exact Usage Ratio 5. Percentage Based Calculator Efficiency Calculators: 1. Fuel Efficiency Conversion 2. L/100km Calculator 3. Miles Per Gallon (MPG) Calc Area Converters • Square Inches and Shorter Conversion • Square Feet & Yards & Meters Conversion Distance Converters • Inches & Centimeters & Millimeters Conversion • Feet & Yards & Meters Conversion • Nautical Miles, Statue Miles and Kilometers Conversion Volume Converters • US/Imperial to Metric Units Conversion • Metric to US/Imperial Units Conversion • Inches & Centimeters Volume Conversion • Feet, Yards, & Meters Volume Conversion ... and Temperature Conversion Values calculated can be in US Gallons for Gasoline, Imperial Gallons for Petrol, or Liters. If you are uncertain of the need for a mixture, please consult your owners manual. It is not recommended to add oil to the fuel of 4 cycle engines. This app features: • Send your calculations or conversions by email • Universal App (iPhone and iPad) • Fast app switching • Automatically Saves Your Inputs • Latest version of iOS is supported • All iPhone screen sized are supported No network connectivity required.
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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
AsyncStorage
TypeScript
Shadcn/ui
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.
