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.
Speldosa (Wintergatan Music Box) is an Audio Unit instrument, the result of a unique collaboration between Klevgrand and the Swedish artist Wintergatan/Martin Molin
$4.99 · 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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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 Speldosa: 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 social sharing options compared to competitors.
Validate with people who use this workflow before building.
Hypothesis 2
Assumption to check: No offline listening mode without subscription.
Validate with people who use this workflow before building.
Hypothesis 3
Assumption to check: Lack of personalized recommendations.
Validate with people who use this workflow before building.
Hypothesis 4
Assumption to check: Limited customization options for playlists.
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.
Speldosa (Wintergatan Music Box) is an Audio Unit instrument, the result of a unique collaboration between Klevgrand and the Swedish artist Wintergatan/Martin Molin. Wintergatan has primarily worked in the physical world (the Marble Machine is probably the most astonishing example), while Klevgrand has performed its craft within the digital sphere. When these two worlds now meet, the result is something that both visually and aurally inspires the creation of new compelling melodies. Speldosa (Swedish for “Music Box”) is the essence of the shared beliefs of Klevgrand and Wintergatan, and their fascination with minimalism. A simple melody played on a music box can contain an equal amount of emotional power as any symphonic work. There is something about the music box sound that never ceases to fascinate. The instrument itself has been meticulously recorded by Wintergatan and transformed into a playable digital instrument plugin. It features four different models (Modern, Vintage, Antique, and Eternal = Reversed), two different Room models, and an algorithmic reverb. Wintergatan about Speldosa: "I created the sound by sampling a music box using an acoustic guitar as resonance box. I chose the best samples and it was instant magic. The Music Box went on to become the sonic signature for my two bands, Detektivbyrån and Wintergatan, both recognised for their unique sound. The Speldosa has been the secret sauce in my music career and i hope other musicians finds it as useful as i have. There is a special quality to this exact music box sound that lifts it above the novelty feeling of a toy and turns it into a real music instrument. It just sounds so good, that’s really it. And it is a sound that makes you write music instantly - the music comes from the sound itself. During the collaboration with Klevgrand, when they sent me the first beta version of the plugin, i ended up playing around with the sound for three hours, losing track of time. I wrote three songs that day when i was scheduled to actually do something else. That’s what the sound does to me, and i think it will do the same for others." Features: - Four different music box characters - Two room ambiences - Spacious reverb - Optional vibrato - Output level Speldosa works both as a standalone app and as an AUv3 plugin. Check out the product web page for more info, sound examples and a user manual. Feedback or suggestions? Drop us a mail: support(at)klevgrand.se or @klevgrand on Twitter.
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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.