Duo Explorer

What an app can do on iPhone Duo, in every pose. → dalmaer.github.io/duo

The iPhone Duo folds: an outer display for when it is shut, and an inner display that opens to twice the width — flat, half-folded like a book, set down like a tiny laptop, or stood on its edge facing someone. Duo Explorer is a catalog of example apps running on an emulated Duo you can put in each of those poses, so you can see what an app should do when it is closed, open, standing, or on the table.

Start with the Cajón: set the Duo down in table pose, play the flat bottom half like the drum's front plate, and watch the instrument answer on the standing top half — #cajon/table.

Music	Games	Retro	Productivity	Learning	Patterns
CajónCrate SamplerAccordionMusic BoxDJ Decks	BattleshipsHinge GuessPinballPokerChompFishingMini-golf	Pocket ConsoleDuo-ManCritterdexSplit-flap ClockEtch-a-sketchTypewriterPocket PalInstant Camera	E-ink ReaderSketchbookTranslatorTeleprompterRecipePlanner	Fold CardsPop-up StorybookQuiz BuzzersAnatomy Layers	List and DetailWatch Above, Play BelowSubject PreviewLaptop EditorOverlay Map

Every example says what it does in each pose, names the Apple guideline it demonstrates, and credits whoever had the idea first. See SPEC.md for the whole design, and docs/research/sources.md for the posts and repos it draws on.

Poses

	Pose	Display	Size classes
▯	Closed	outer	compact / regular
▭	Closed · landscape	outer	compact / compact
◫	Open	inner, fold vertical	regular / regular
⊟	Open · portrait	inner, fold horizontal	regular / regular
📖	Book	inner, partly folded, 30–175°	regular / regular
💻	Table	inner, partly folded, bottom flat	regular / regular
⛺	Standing	inner, stood on its edge — the outer display faces the other person	regular / regular

Run it

npm install
npm run dev        # http://localhost:5173/duo/
npm run check      # tests, typecheck, roadmap, build — what CI runs

Node 24 (.nvmrc). No framework and no runtime dependencies.

Add an example

One file in src/examples/, one line in src/examples/index.ts. The contract is src/core/example.ts and the reference is src/examples/cajon.ts. Agents: the duo-explorer skill walks through it, and the apple-hig skill has Apple's rules. Ideas waiting to be built are issues labelled example.

How the work is run

Phases, each with its status in its own front matter → docs/ROADMAP.md (generated). Every unfinished phase has a GitHub issue, and every issue is on the duo project board. Design options live on the project's isocan canvas (.isocan/project.json) and in docs/design/. Working rules for people and agents: AGENTS.md.

Credits

Ideas from @viditb (Duo-Man), @javilosana, @MiruDaws, @MarioSaputra, @elvin_not_11, @stvnzhangshuhan (CRATE), @acooldora, @anshuc, and erkamyaman/hinge-guess. Apple's guidance via justinwetch/HIGAgentSkills. Cajón voices and grooves from Ritmo (dalmaer/cajones). All examples are original reimplementations; no one's code or art is copied.