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
Harry's Dyno
Harry's Dyno is a high precision performance measuring app
$3.99 · In-app purchases
PRICE
$3.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 1.0
2 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.
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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 included18 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 Harry's Dyno: map the core Sports 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
Incorporate social sharing and challenges.
Assumption to check: Lack of user engagement features.
Validate with people who use this workflow before building.
Hypothesis 2
Provide detailed analytics and comparisons.
Assumption to check: Poor performance tracking and insights.
Validate with people who use this workflow before building.
Hypothesis 3
Expand workout categories and customization.
Assumption to check: Limited workout types.
Validate with people who use this workflow before building.
Hypothesis 4
Add forums or groups for users to connect.
Assumption to check: No community interaction.
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
Harry's Dyno is a high precision performance measuring app. It utilizes GPS and OBD sensor input to recognize arbitrary speed ranges like 0-60 mph or 100-200 km/h. Both acceleration and deceleration testing is supported. Results can be compared and analyzed in details. Using two-cursor mode, one can inspect subranges of data recorded (e.g. 80 to 120 km/h for a 0 to 200 km/h). Data is stored locally and can be filtered by speed range and vehicle used. It can be exported to various data formats too. Provided the smartphone is mounted in a position with good GPS accuracy, the internal GPS can be used for measurements. For short speed ranges, high powered vehicles, and highest precision, either external GPS or OBD sensors can be connected. OBD adapters are actually preferable as speed changes are available instantly. We have an always up to date list of compatible accessories available here: www.gps-laptimer.de/compatibility/ios For distance based performance testing (quarter mile etc), please use Harry's LapTimer currently. This mode will be added to Harry's Dyno as a free upgrade shortly. For Harry's LapTimer users! Harry's LapTimer GrandPrix has received a free feature upgrade and includes Harry's Dyno functionality now: please follow LapTimer ‣ Race ‣ Performance to use the dyno mode. In case you have used Harry's LapTimer Petrolhead so far, you may either upgrade it to GrandPrix (LapTimer ‣ Administration ‣ Add-ons), or go for Harry's Dyno as a separate app. Enjoy and let us know what you think! For questions, tipps & tricks, and support, please use our forum www.gps-laptimer-forum.de
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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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Axios
BUILD KIT DIFFICULTY
Advanced
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.
