はいいろの森
Free · play online in your browser, no download
A short 2D RPG about a forest losing its colour, made in one day from the request “make an RPG”. The developer says no human wrote a line of its code.
Official site hakuzin-ai.github.io, verified Nov 3, 2026. Linked as the play address from the repository README (hakuzin-ai/ai-rpg) and from the developer's own Zenn article, which also links the repository.
Where to play
Every platform this game is on. Links are checked against official sources; we never host or mirror games.
- Play free — official siteBrowserReleasedFree
Runs in a desktop browser. No download.
Browser (no download) · Official link verified Nov 3, 2026.
About はいいろの森
はいいろの森 (Haiiro no Mori, “the grey forest”) is a free, short 2D role-playing game for desktop browsers. A forest that was once full of colour has started to fade to grey, a growl echoes from its depths, and Riko, an apprentice mage, sets out with a small staff entrusted by the master to bring the colour back. You walk one tile-based map from south to north: the winding path is safer, with fewer and weaker monsters, while cutting across the grass is shorter but brings more and stronger random encounters. Battles are turn-based, with Fight, Fire (costs MP and ignores defence) and Run; you gain experience and levels, two springs restore HP and MP, and a boss waits at the altar at the end. A first run takes about 10 to 18 minutes. It needs a keyboard (arrow keys or WASD, Z or Enter) and has no touch controls, and it is in Japanese. It is an experiment by the developer, who writes as “おじさん” (ojisan_ai_lab): the only brief was “make an RPG”, and Claude Code agents chose the setting, title, story, systems and balance and wrote all of the code, with a development journal counting every failure; the developer says no human wrote a line of code. Graphics are Kenney CC0 tiles plus a title background generated locally with AI. Free on GitHub Pages; the repository is public.
How it was built
VerifiedThe developer's Zenn article (5 Aug 2026) says the game was made in one day with zero lines of code written by a human, from a brief of “RPG作って” (make an RPG). The repository's CLAUDE.md and Claude Code settings define the setup: a main session acting as project manager on Fable 5 (.claude/settings.json) that plans, hands work out, checks it in the browser and keeps the journal, and dev and reviewer sub-agents fixed to Opus 5 (.claude/agents). Per the article, the human only gave the one-line request, approved the AI's proposed scope, and played the finished game and gave four pieces of feedback; an AI in a parent project researched the technical route, set up the repository skeleton and wrote the CLAUDE.md rules. The journal counts 12 failures, 12 self-fixes and 0 human interventions up to v1.0, and 14 failures, 12 self-fixes and 0 human interventions up to v1.1, the version revised after the developer's playtest.
- DeveloperREADME: an experiment to make a playable 2D RPG with AI alone, without a human writing a single line of code; v1.0 is the result of the initial instruction only, v1.1 the AI's one revision after a human playtest, with still zero lines of human implementation. — GitHub
- DeveloperDevelopment journal (logs/journal.md): every FAIL, SELF-FIX, HUMAN and DECISION entry from 4 Aug 2026, including the v1.0 tag and the v1.1 changes. — GitHub (hakuzin-ai)
A Claude Code project-manager session (Fable 5) with dev and reviewer sub-agents (Opus 5), working from a CLAUDE.md that fixed the scope (one map, random encounters, turn-based battles, levelling, one boss, a 10 to 20 minute run), banned declaring work done without checking it in a browser and required a journal entry for every failure. When no browser preview tool was available, the agents drove a cached Chromium over the DevTools protocol for key presses, console logs and screenshots. Phaser 4, Vite and JavaScript; balance was tuned with 2,000-run simulations. Assets went from placeholder shapes to Kenney CC0 tiles, plus one title background generated locally with ComfyUI.
- Engine / framework
- Phaser
- Languages
- JavaScript
- Team size
- Not disclosed
- Initial build time
- One day (4 Aug 2026), to v1.0 and the v1.1 revisionDeveloper ReportedGitHub (hakuzin-ai)
- Development time
- Not disclosed
- Development cost
- Not disclosed
- AI-written code
- ~100% of shipped codeDeveloper ReportedZenn (おじさんAIラボ / ojisan_ai_lab)
“作らせたのは2D RPGです。1日で、人間が書いたコードは0行。”- バイブコーディングすらしない (developer's Zenn article, Japanese)
- Source and development journal on GitHub (hakuzin-ai/ai-rpg)
Verification notes: AI use, roles and failure counts come from the developer's Zenn article (published 5 Aug 2026, 09:16 JST), read through Zenn's API on 6 Nov 2026, and from the repository's README, CLAUDE.md, .claude/settings.json, .claude/agents files, docs/SPEC.md (the non-spoiler setting, controls and battle rules) and logs/journal.md, read through raw.githubusercontent.com the same day; the README links the play address, which loaded. The “0 lines” claim and the counts are the developer's own and, as the article notes, the FAIL and SELF-FIX labels were assigned by the AI itself. The article says the game needs a keyboard and has no touch controls. The developer writes in the first person as “おじさん” and links the GitHub account hakuzin-ai; no real name is given. When the game first went public is not stated, so no release date is recorded: CLAUDE.md says pushes happen only on the developer's instruction, and the journal dates the build to 4 Aug 2026. The game's scripts contact no AI services. Stars were not checked (github.com was not reachable from our checker). The English alternative title is our romanisation of the README heading “AI RPG『はいいろの森』”; the game has no official English title.
Development history
Built in one day: the specification, five milestones and the v1.0 tag, then the v1.1 revision after the developer's first playtest (level cap raised from 6 to 8, a new sprite for Riko, fewer encounters off the path, a message-box fix), per the journal.
DeveloperGitHub (hakuzin-ai)The developer publishes a Zenn write-up with the failure counts and the play link.
DeveloperZenn (おじさんAIラボ / ojisan_ai_lab)
Game performance
Each figure measures something different — concurrent players, owners, downloads and sales are never interchangeable and are never added together. Labels show where each number comes from.
Browser (official site)
No public metrics recorded for this listing.
Not publicly available: Concurrent players (site), Monthly revenue, Gross revenue.
Sales & revenue (all platforms)
Browser game — there are no downloads to count.
Reviews & rankings
Not yet reviewed by our editors.
Not currently ranked.
Sources
| Source | Type | Published | Accessed |
|---|---|---|---|
| バイブコーディングすらしない ― AIに「RPG作って」の一言でゲームが完成した話 Zenn (おじさんAIラボ / ojisan_ai_lab) · Japanese | Devlog | Aug 5, 2026 | Nov 3, 2026 |
| hakuzin-ai/ai-rpg (README, CLAUDE.md, docs/SPEC.md) GitHub · Japanese | Repository | Not confirmed | Nov 3, 2026 |
| ai-rpg development journal (logs/journal.md) GitHub (hakuzin-ai) · Japanese | Repository | Not confirmed | Nov 3, 2026 |
| Official game page (language check) おじさん (ojisan_ai_lab) | Official site | Not confirmed | Nov 3, 2026 |
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