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
OilField Formulas iHandy Calc
------- Updated
$1.99 · In-app purchases
PRICE
$1.99
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's included17 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 OilField Formulas iHandy Calc: map the core Reference 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
Expand formula database to include more industry standards.
Assumption to check: Limited formula selection compared to competitors
Validate with people who use this workflow before building.
Hypothesis 2
Invest in user-centered design to improve navigation and readability.
Assumption to check: Poor user reviews indicate bad UX/UI
Validate with people who use this workflow before building.
Hypothesis 3
Clarify purchase options and provide a free trial.
Assumption to check: In-app purchase confusion
Validate with people who use this workflow before building.
Hypothesis 4
Create a help section with FAQs and tutorial videos.
Assumption to check: Lack of user support or documentation
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
------- Updated. Added more than 250 oilfield calculators ------- Aims of this application to make ease the life of Oilfield specialist and Petroleum, Mud Engineers by providing correct hand calculations. It is meant for Engineers,Specialist who are involved in Oil and Gas exploration and Drilling. This application is an essential supporting tool. P.S.: Best way for correct calculation is the hand calculation. Application builded by last updated API (American Petroleum Institute) Data. -Capacities & Volumes for Downhole formulas -Capacities & Volumes for Tanks formulas -Pump Output & Rate -Pump Press.Relationships -Equivalent Circulating Density (ECD) -Trip Calculations -Pressure & Gradient -Kill Sheet Calculations -Kick Related -Kick Related Engineering -Volumetric Method calculation -Lubricate & Bleed -Bullheading Calculations -Stripping/Snubbing -Subsea -Accumulator Sizing -Mud & Cement -Hydraulics -Tripping Rules of Thumb -Stuck Pipe -Free Point & Stretch Estimates -Estimating Temp. Drop Across a Choke or Orifice -Bit Nozzle Pressure Loss -Estimating Gas Well Flow Rates -Area of a Circle -Force & Pressure -Weight of Spiral Drill Collar -Buoyancy Factor (BF) -Surface & Bottom Hole Pressure in Full Gas Column -Pipe Elongation and more formulas... Also this app has: -Coiled Tubing Stretch Table -Mud Weights properties -Acronyms & Abbreviations -Conversion Factors -Constants -Drillpipe capacity and displacement -Drill Collar Capacity and displacement -Casing Capacity -Hole Capacity and more information… Good Luck in Your Job!!! ---------------------- Other best oilfield apps in App Store: - Annular Volume Calculator; - Casing make-up Torque Chart; - Surge & Swab Pressure Calc; - PDC Bit & Drilling Calculator; - Kick Tolerance Calculator; - ASTM Tables: 54A, 54B, 54D; - and MORE... ---------------------- Follow us: Instagram: @NationalOilfield Facebook: @OilfieldTeam
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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.
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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.
