Mobile App Development for Productivity & Health
Portfolio of independent developer Yang Sun, featuring Handwriting Book, PrivAI, Life Cabinet and more.
Featured Applications
Each app is carefully designed to improve your quality of life
QuickNotes Flashcards Watch
Effortless Exam Prep and Study
A flashcard note app designed for exam review and knowledge accumulation, supporting seamless sync between iPhone and Apple Watch.
PrivAI LLM - Local AI Chat
Local Offline LLM AI Chat
An intelligent application based on DeepSeek-R1 distilled models, designed for users who value privacy, convenience, and versatility.
Life Cabinet
Manage Your Life Blueprint by Departments
A comprehensive life planning and growth management tool that coordinates health, finance, career, learning and other aspects through departmental management.
Copybook
Handwriting Focus & Calm
A digital space for mindfulness through handwriting, helping you regain focus and calm.
R90 Sleep Assistant
Manage Your Sleep Cycle
Based on the R90 sleep method, helping you plan sleep by cycles, eliminate sleep anxiety, and regain energy.
Self-Love Project
Stop Self-Hate, Start Self-Love
Stop hating yourself into improvement. Use 'Identity Switching' rituals and a 21-day challenge to become your better self with love.
GeoFlow
Geo Arbitrage & Budget
Turn the world into your wallet. Multi-currency budgeting and geo-arbitrage analysis tool designed for digital nomads.
Rich Dad Finance Tracker
Build Assets, Not Just Budgets
A financial tool based on 'Rich Dad Poor Dad' principles, helping you distinguish assets from liabilities and focus on cashflow and passive income.
PetSitter Pro: Client Manager
Schedule, Invoice & Reports
Designed for independent pet sitters and dog walkers, helping you turn from 'amateur part-time' to 'industry expert'.
SkillHub: Discover AI Skills
Find & Save Pro Agent Skills
Build AI-driven businesses with 150+ ready-to-use skills. No coding, three-step setup.
Blog
Sharing iOS development experience, ASO tips, and product design insights.
Installed 100 AI Skills But Still Can't Use Them? 5 Myths of 2026
You bookmarked 50 skills on GitHub, downloaded 150 workflows, but has your AI efficiency actually improved? In 2026, AI skill libraries became the new obsession, but most people install skills without knowing how to use them. Today we cover 5 big myths: treating skills like prompts, downloading without organizing, believing in universal skills, ignoring workflow integration, building in isolation. The right approach isn't collecting 1000 skills—it's curating 10 that suit you best and using them to the extreme.
Read more40,000 New Facial Palsy Cases Every Year — Yet Only 1% Have Access to Evidence-Based Rehab Tools
1.5–3.2 million new facial palsy cases globally each year, yet most patients lack structured home rehab tools. This article reveals this overlooked digital health market and how iPhone TrueDepth is changing facial palsy recovery.
Read more5 Common Myths About Facial Palsy Recovery: Acupuncture, Electrical Stimulation, and Hard Exercise — You Might Be Doing Them All Wrong
Sooner acupuncture = faster recovery? Harder exercise = better? Electrical stimulation helps? At least 3 of these 'reasonable-sounding' facial palsy methods may slow your recovery or cause permanent synkinesis. This article debunks 5 myths and reveals what actually works.
Read moreSmiling Makes Your Eye Squint? Synkinesis After Facial Palsy Explained
Smiling makes your eye squint? Closing eyes pulls your mouth? That's synkinesis — affecting 40%–60% of facial palsy patients. Learn why it happens and 3 clinically-validated training principles to manage it.
Read moreAbout Indie Developer Yang Sun
As an independent developer focused on mobile apps, I believe technology should serve life, making complex things simple and beautiful experiences accessible.
Since starting iOS development in 2020, I have released 55 apps covering productivity, health, learning, and more. Each app embodies my pursuit of user experience and product quality.
User Experience
Every detail carefully polished
Innovation
Following trends, exploring possibilities
Service
Listening to feedback, improving constantly