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.
4:20 is an SMPTE LTC timecode reader and generator for iPhone and iPad
$4.99
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.
A product spec, screen plans, and build steps for your coding agent.
First kit free with a verified email
Combine features and design from your favorite apps.
Your first Build Kit is free with a verified email.
Generating… usually about a minute.
What should your app do differently? Your note travels with the kit so your coding agent builds around your idea.
A product spec, phased build plan, differentiation notes, and screen references.
Illustrative example: an invoice app for independent contractors. Your kit is tailored to the app you choose; this is not its generated content.
Goal: Send a clear invoice after finishing a job.
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.
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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Good fit for mobile-first iOS and Android prototypes with managed app scaffolding.
Rork plan preview for 4:20: map the core Photo & Video workflow, choose the smallest differentiated feature set, define the data and monetization boundaries, then prototype the riskiest user journey first.
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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
Assumption to check: Limited editing features compared to advanced apps
Validate with people who use this workflow before building.
Hypothesis 2
Assumption to check: No cloud backup for edits
Validate with people who use this workflow before building.
Hypothesis 3
Assumption to check: No user community or sharing options
Validate with people who use this workflow before building.
Original App Store material. Ratings and screenshots describe the existing app, not proof of demand for your version.
4:20 is an SMPTE LTC timecode reader and generator for iPhone and iPad. It reads timecode from a wired audio input and shows lock, frame rate, drop frame, measured rate, direction, and level. It can generate LTC at the same time, over the same connection. The reader is made for troubleshooting. When a rig will not chase, plug into the line and check the code where you stand: the rate as measured against what the source claims, drop frame or not, which direction it is running, and how hot the line is. Mislabeled rates, code that should have stopped, and low or clipping levels all show up in the first few seconds. Between cues, it works as a confidence monitor on any line you need to trust. The screen does not sleep while a mode is running, and timecode keeps going when you switch to another app. Checking a message does not stop the code. READER • Lock state and a full readout: frame rate with drop frame flag, measured rate, direction, level • Runs continuously and keeps reading through route changes and interruptions • Keeps reading in the background while you use another app • If iOS takes the audio session away, the readout dims and says so instead of holding stale numbers GENERATOR • 23.976, 24, 25, 29.97 drop frame, and 30 fps • Start from any timecode, or generate time of day • Output level control, with left, right, or both channel routing • Anchored to the system clock, so long runs hold their time • Keeps generating in the background while you use another app • Runs alongside the reader for loop-through checks • Warns before sending LTC to a speaker, Bluetooth, or AirPlay, and requires a press-and-hold to override REQUIREMENTS A wired audio connection: a class-compliant USB audio interface, or a headset-jack adapter with a line input. There is no microphone mode. This version reads and generates LTC only; MIDI timecode is not supported. PRIVACY No account, no analytics, and no network connection. Nothing leaves the device. Made for production sound, playback and show control, video engineering, DIT carts, and broadcast maintenance.
Written user reviews are not shown here. Check current App Store reviews >
Plan a focused first version with your coding agent. These are planning assumptions, not a delivery guarantee.
Choose one audience and one core workflow. Use the kit to agree on its screens, data, and acceptance criteria before building.
Decide which secondary features, integrations, and platform support can wait. Your version does not need to reproduce everything in the original.
Validate external services, specialist technology, data access, and ongoing costs for your chosen scope.
Not assessed in a Build Kit yet.
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.