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.
ThumbJam is a powerful musical performance experience
$8.99 · In-app purchases
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.
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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 ThumbJam: map the core Music 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 instrument selection compared to other apps
Validate with people who use this workflow before building.
Hypothesis 2
Assumption to check: Steep learning curve for new users
Validate with people who use this workflow before building.
Hypothesis 3
Assumption to check: Audio latency issues when playing instruments
Validate with people who use this workflow before building.
Hypothesis 4
Assumption to check: Lack of collaboration features
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.
ThumbJam is a powerful musical performance experience. You get over 40 high-quality real instruments multi-sampled exclusively for this app. Hundreds of included scales allow you to effortlessly play in any style from rock to classical, whether you are a musical novice or a seasoned professional. ---====--- Jordan Rudess, the world-renowned keyboardist for Dream Theater says: "ThumbJam stands at the very top of the overcrowded music app world. The sounds included absolutely rival those found in pro instruments and making music on the app is a total joy. The only problem I have with this app is that I did not make it myself! Luckily, I'm able to work with the developer and offer a few good feature ideas as well as some choice sounds from my personal collection!" ---======---- Even if you've only played air guitar, ThumbJam lets you sound like a pro. Pick an instrument and jam -- with all the scales to choose from you'll never hit a wrong note. The high quality instrument samples will make you sound like you just skipped years of music lessons. For the performing musician, this app is awesome for soloing on an instrument you didn't bring along. Play in any key, any style -- go from a string ensemble to a wailing guitar. ThumbJam was developed and tested by musicians to feel and sound like a real instrument. You'll be surprised at how expressive it can be, make sure to check out the videos and audio at thumbjam.com. ThumbJam makes use of tilt and shake to add vibrato, tremolo, note bends, and volume swells for more realistic and expressive results. It supports up to five (eleven on iPad) simultaneous touches and up to 32 voice polyphony, for each of up to 8 loaded instruments! Delay and stereo reverb add depth to the sound, and a resonant lowpass filter gives you more tone shaping power. Put on your headphones or plug in to your home stereo to experience some of the highest quality instruments in the App Store, even after all these years! Build your own loops from the ground up or import your favorites and jam from there. Layer as many loops as you want, with different instruments for each. Export your loops as audio files via WiFi. Copy and paste audio from other apps using AudioCopy/Paste as well the general pasteboard, via email, AudioShare, iTunes Document Sharing, Files, or open directly in another application. Supports Audiobus and InterApp Audio for streaming sound to/from other apps in real-time, including state save/restore with Audiobus 3. Extensive MIDI input and output support over WiFi or Bluetooth, with any CoreMidi compatible device, or other apps on the same iOS device with virtual MIDI. Now also supports Ableton Link for tight sync between apps on the same network. Supports MPE input and output (and did so before it was even a thing)! New powerful arpeggiator feature lets you play patterns with perfect time sync, from the screen or via MIDI control. The app includes a huge variety of scales, from western to eastern. Save your favorites for quick access, or create your own in-app. You can even import new scales in the Scala format for complete flexibility. You can also record your own multi-sampled instruments using a built-in or attached microphone, or from file import. Included instruments: + Cello, Violin, Viola + Upright Bass (plucked and bowed) + Several drumkits + Darabukka + Djembe + Electric Guitar + Electric Bass + Trumpet + Trombone + Tenor Sax + Flute + Low Whistle + Acoustic Guitar + Hammered Dulcimer + Mandolin + Cittern + Grand Piano + Drawbar Organ (2 types) + Rhodes + Pipe Organ + Synth Strings + Synth Choir + Theremin + Sawtooth Waveform + Sine Waveform + Triangle Waveform And from Jordan Rudess: + JR Zendrix + JR Smooth Steel Many more for immediate FREE download in the app including several drumkits, Mellotron, basses, banjo, tabla, ukelele, guitars and more! Go to the Sound menu under Download Samples....
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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.
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.