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
Trill: Ear Training Daily
Learn to hear music
Free · In-app purchases
PRICE
Free
In-app purchases
BUSINESS MODEL
Freemium
No overall Grossing estimate available
RATING
★ 4.5
1,119 ratings · Top 15%
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/
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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 Trill: Ear Training Daily: 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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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
Expand the exercise library with more challenging options.
Assumption to check: Limited variety of exercises for advanced users
Validate with people who use this workflow before building.
Hypothesis 2
Add options for sharing progress on social media.
Assumption to check: No social sharing features
Validate with people who use this workflow before building.
Hypothesis 3
Ensure UI consistency for a more polished look.
Assumption to check: Inconsistent user interface across screens
Validate with people who use this workflow before building.
Hypothesis 4
Introduce AI-driven personalized training based on user performance.
Assumption to check: Lack of personalized training plans
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
Learn to hear music. Not guess it. Have you ever wanted to play music by ear, recognize chords instantly, or identify the key of a melody? A trained musical ear changes everything. It helps you improvise, compose, transcribe melodies, sing in tune, and play with others confidently. Your musical ear is like a muscle. If you don’t train it, it stays weak. If you train it a little every day, it becomes instinct. Just 10 minutes of daily ear training is enough to build powerful musical hearing over time. Short, focused sessions train your brain to recognize tones, chords, and keys naturally — the same way athletes build strength with consistent workouts. And if you struggle with consistency, Trill makes you serious about it. With Focus Lock enabled, distracting apps are blocked until you complete your daily ear training. No scrolling first. No excuses. You train your ear — then you unlock your screen time. Train first. Scroll later. Funny part is, that Trill turns ear training into a game you actually want to come back to. Daily challenges, streaks, levels, and collectible badges transform serious ear training into a motivating system. Many users describe Trill as “Duolingo for ear training” — short sessions, clear progress, and constant small wins that keep you practicing. I originally built Trill for myself. I wanted to improvise more freely, hear the key of a song instantly, and recognize chords during jam sessions without guessing. What started as a personal tool became a complete daily training system for everyone who want real musical hearing. Free and Pro Features Free access includes an essential musician toolkit such as a tuner, metronome, and chord, interval, and scale visualizers. A free trial provides limited access to ear training and vocal training. Trill Pro unlocks unlimited training, advanced exercises, progress tracking, achievements, and Focus Lock. By downloading or using Trill, you agree to our Privacy Policy and Terms of Use. Privacy Policy: https://trill.studio/privacy-policy Terms of Use: https://trill.studio/terms-of-service
Written user reviews are not shown here. Check current App Store reviews >
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
Zustand
react-native-reanimated
expo-linear-gradient
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.
