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
Fetal BCN Calculator
iFetal is an application aimed at specialists in fetal medicine.
$13.99 · In-app purchases
PRICE
$13.99
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 included16 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 Fetal BCN Calculator: map the core Medical 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 reminders or notifications for calculations
Assumption to check: Limited user engagement features
Validate with people who use this workflow before building.
Hypothesis 2
Offer more value through features or free trials
Assumption to check: High price point for users
Validate with people who use this workflow before building.
Hypothesis 3
Integrate forums or help sections for user interaction
Assumption to check: Lack of community support
Validate with people who use this workflow before building.
Hypothesis 4
Include validation and educational content to enhance trust
Assumption to check: Potential for inaccurate 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
iFetal is an application aimed at specialists in fetal medicine. It provides different calculators in the following areas: - Gestational - Doppler - Fetal Anemia - Preeclampsia - Fetal Growth - Congenital Diaphragmatic Hernia The different calculation algorithms are based on multiple research studies: Dating 1. Robinson HP. A critical evaluation of sonar ‘crown-rump length’ measurements. BJOG 1975;82:702-710. Revised BUMS sept 2008. 2. Mul T. A comparative analysis of second-trimester ultrasound dating formulas in pregnancies conceived with artificial reproductive techniques. UOG 1996; 8:397-402. 3. Mongelli M. Third trimester ultrasound dating algorithms derived from pregnancies conceived with artificial reproductive techniques. UOG 2005; 26:129-131. Fetal Growth 1. Hadlock FP. Estimation of fetal weight with the use of head, body and femur measurements a prospective study. Am J Obstet Gynecol 1985;151(3):333. 2. Hadlock FP. Sonographic estimation of fetal weight. The value of femur length in addition to head and abdomen measurements. Radiology, 1984 Feb; 150(2):535. Growth centile in II TM 1. Pedersen N, Figueras F, Tabor A. Obstetrics and Gynecology 2008; 112(4):765-71. Unique percentile in III TM 1. Figueras F. Customized birthweight for a Spanish Population. EJOGRM 2008; 136(1):20-4. Multiple percentile in III TM 1. Kuno A. Comparision of fetal growth in singleton, twin and triplet pregnancies. Hum Reprod 1999. 2. Corbes de referència de pes, perímetro craneal i longitud en nèixer de nounats d'embarassos únics, bessons i trigèmins a Catalunya. Departament de Salut. Generalitat de Catalunya 2000. Congenital Diaphragmatic hernia 1. Jani J, UOG 2007; 30:67-71. 2. Dekoninck P, BJOG 2015; 122:940-946. Normal Doppler Values 1. Arduini D J Perinat Med 1990; 18:165. 2. Baschat AA UOG 2003; 21:124. 3. Mari G N Engl J Med 2000; 342:9. 4. Hecher K UOG 1994; 4:381. 5. Rizzo G UOG 1996; 7:401. Biometrías óseas CC: Snijders RL, UOG 1994. Extremidades: Chitty, LS BJOG 2002. Aplicación desarrollada por Medicina Fetal Barcelona
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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
Supabase
React Navigation
Zustand
react-native-paper
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.
