Turning a phone hinge into a fishing rod: building Fold Fish

JPUI — Wed, 11 Nov 2026 06:55:19 +0000

I'm Jan. I make games as JPUI, and Fold Fish is a fishing game for iPhone Duo — Apple's foldable. The short version is this: the hinge is the control. There is no joystick. The fold is the fishing rod.

A fishing rod already works a bit like a hinge. You open it back to load the cast, then you send the line out. That motion was sitting in the hardware. So the design started there, not with a virtual stick in the corner of the screen.

How wide you open the fold sets how far you cast. A tap sends the line into the pond. Hold, and you reel — while dodging the other fish. Three moves. That's it.

The game is built on the iPhone Duo hinge API, UIHinge. I don't have a long technical war story to tell about that, and I won't invent one. The work that interested me was making the phone feel like a rod, then getting the interface out of the way.

A pond across the fold

In book mode, the pond spans the unfolded screen. Fish swim right across the hinge. It's a living pond, from sunrise to stars — day and night on the same stretch of water. You hook something, you land it, you fill in a catch atlas: catch and discover every species. Along the way there are coins, helpers, and Foldfish Gold.

The App Store listing puts the wildlife mildly: dozens of fish — and a few surprises.

The same game on a phone that doesn't fold

Most iPhones still don't have a hinge. Fold Fish has to work there too.

On a regular iPhone, on-screen controls do the same job. I didn't want the non-foldable version to feel like a demo of the "real" one, or like an apology for missing hardware. It should just be a fishing game you can play on any iPhone. The Duo is where the hardware finally matches the metaphor. Everywhere else, the buttons stand in for the fold.

It requires iOS 18. It's free, with optional in-app purchases. No ads. I don't collect data from the app. Version 1.0.2, from 23 October 2026, is localized in 30+ languages.

Sometimes the catch is not a fish

I like a fishing game that can be cozy without being precious. The humour lives in the catch cards, and in what the fisherman says when the pond does something rude.

There's a moment in the gameplay where two fish bump into each other underwater, and he reports it like a traffic bulletin: "Bum. Dopravní nehoda pod hladinou." Boom. Underwater traffic accident.

And one of those atlas surprises is a frog. Land it, and the card reads: "PERFEKTNÍ! Žába — Tohle není ryba. Žába to ví. Ty teď taky." That's "Perfect! Frog — This isn't a fish. The frog knows. Now you do too."

The card doesn't really congratulate you. It just corrects you, politely. The joke doesn't need explaining. If you hook a frog, you already know.

Out in the world

On 2 November 2026, iGeeksBlog featured Fold Fish in a YouTube video. If you'd rather see the fold-to-fish motion than read about it, start there — or here:

Fold Fish

Fold Fish on the App Store

If you have an iPhone Duo, open it like a rod and see how far the line goes. If you don't, the on-screen controls are waiting.

Introducing Foldsplat — a game built for foldable iPhones

JPUI — Mon, 09 Nov 2026 17:30:55 +0000

I'm Jan, a solo indie iOS developer from Czechia (studio JPUI).

My first shipped game is Foldsplat. It's built for foldable iPhones (iPhone Duo / Fold): bugs crawl across both screens, you slam the device shut, and the cover display shows an x-ray of the splat. The hinge is the mechanic, not a stretched iPhone layout.

It's free on the App Store. Site and more screens: jpui.cz/foldsplat.