Individual Developer Studio

A little lab for
nights and weekends.

Tools that remove everyday friction, and windows that make you look up at space.
Built one by one, whenever something feels exciting.

What's New

What's New

2026.09 ReleaseLaunched YOIZAKURA — a side-scrolling action game about the walk home from school. The goal is not to defeat everything, but to carry supplies back to your sister. Play it → NEW
2026.09 UpdateStarted a blog — how things work and why I build them, written to be found by search. Japanese only. Read it →
2026.08 ReleaseLaunched FAMILY NOTE — record what your relatives were actually like. Comes with a family tree and a single-HTML export that outlives the app. Try it →
2026.08 ReleaseLaunched MOKUROKU — sort what you like and dislike into cards. Self-analysis that never scores you. Try it →
2026.07 ReleaseLaunched FLOW KAKEI — a no-guilt household budget app. 3-second entry. Try it →
2026.07 ReleaseLaunched STELLAR ROGUE — a twin-stick roguelite that climbs from low orbit into deep space. Compete on the global leaderboard. Play it →
2026.07 ReleaseLaunched Near Stars — 4,000 real stars within 100 light-years, mapped in 3D. Move through time and watch them drift. View it →
2026.06 ReleaseLaunched Solar System 3D — see the planets right now in real-time 3D. Tap a planet for details, or time-travel. View it →
2026.06 UpdateMajor update to ISS 3D Viewer — orbit prediction, pass forecasts, and EN/JP support. View it →
2026.06 ReleaseLaunched HENSAI — visualize repayment schedules for mortgages, card loans, and revolving credit. Try it →
2026.06 ReleaseLaunched FLOW BASHO — decide where to go together by voting. Try it →
2026.06 ReleaseLaunched FLOW TASK — a GTD-based task manager that keeps you focused on Today. Open app →
2026.06 UpdateAdded a new category: Visualizers.

Products

Products

Polaris Premium ¥300/mo EN / JP

Polaris

Turn vague ambitions into a clear roadmap through AI conversation, then make daily progress just by checking off actions.

  • AI generates mid-term goals and actions
  • Progress bars keep you motivated
  • Monthly review reports, auto-generated
  • Add to home screen (PWA)
Open App →

Tools

Tools

Small, fast, and solving exactly one thing.

FLOW TASK
FLOW TASK
GTD-based task manager. Capture to Inbox, focus on Today — auto-reset every morning keeps you on track.
Free JP only Open app →
FLOW YOTEI
FLOW YOTEI
No sign-up needed. Share a URL and let people pick a time — scheduling made simple.
Free JP only Try it →
FLOW BASHO
FLOW BASHO
Decide where to go together by voting. Add the candidates, share the URL — that's the whole thing.
Free JP only Try it →
SizeKit
SizeKit
Resize & convert images to recommended SNS sizes. Runs entirely in your browser — no uploads, no server.
Free JP only Blog → Try it →
FAMILY NOTE
FAMILY NOTE
Write down what your relatives were actually like — not just names and dates. Person cards, a family tree, and interview prompts. Exports to a single HTML file.
Free JP only Try it →
Browse by genre Work Decide together Money Family & self
See all tools (9) →

Visualizers

Visualizers

Turning real-time data into something you can see.

Near Stars
Near Stars
4,000 real stars within 100 light-years of the Sun, mapped in 3D. Tap a star for details, or move through time and watch them drift.
Free View it →
Solar System 3D
Solar System 3D
See the planets right now in real-time 3D. Tap a planet for details, or time-travel to past and future alignments.
Free View it →
ISS 3D Viewer
ISS 3D Viewer
Real-time 3D view of the ISS position, the Sun and the Moon — with Earth's day/night terminator and the orbital ground track.
Free View it →

Services

Services

Development support for individuals and small teams.

Claude Code Onboarding Support
Help setting up and getting the most out of Claude Code, Anthropic's AI coding tool.
Inquiry Contact →

Playground

Games

Games built for the fun of it — in space, and on the walk home from school.

YOIZAKURA
YOIZAKURA
A side-scrolling action game about getting home. The goal is not to defeat everything but to carry supplies back to your sister — and your bag only holds three slots, so something has to be left behind.
Free Details → Play →
STELLAR ROGUE
STELLAR ROGUE
A twin-stick roguelite that takes you from low orbit to deep space. Pick upgrades to build your ship and face a boss every five waves. Global leaderboard included.
Free Play →

Smaller games built between coding sessions.

Click first to focus · SPACE to jump · Hold for higher jump

Arrow keys or swipe · Merge tiles to reach 2048

JP only Game Center →

Writing

Writing

How things work and why I build them goes on the blog; the process of building alone goes on note. Everything below is written in Japanese.

JP only

Blog

2026.09.07 A light-year measures distance — so why does it keep turning into a story about time? → 2026.09.07 “It should be working” is the most dangerous state — on systems that break without raising an error →
All posts →

note

2026.06.25 I made the Earth spin, and then I couldn't stop → 2026.06.08 Journaling doesn't have to be written well → 2026.06.01 Business frameworks, revisited ④ — DCAP: move first, plan after →
More on note →

About

Who's building this

Kobayan

Kobayan

Tokyo / IT manager by day / indie dev by night

IT manager by day.
Nights and weekends, I build things that spark excitement or help someone solve a real problem.
Most of all, I just love turning ideas into something tangible.

Java Next.js Chrome Extensions Claude Code AI-assisted dev Vibe coding
note → X →