When Apple announced the iPhone Duo I felt the same excitement that I had felt when I got my first iPhone, way back when.

I remember playing Tap Tap Revenge, Fruit Ninja and all those other games that really took advantage of the new hardware to create new experiences. I also loved playing cute puzzles like Cut the Rope and Where’s my water.

A month ago, I got the itch to build something for the duo, in the lineage of those apps. Something that would be a fun puzzle with a unique game mechanic. I started with a simple premise: what if the cover screen was partly transparent? That could make a fun maze that you have to fold and unfold as you solve it.

Orisuji is a turn based paper maze, when the phone is open you have your base maze on the right part of the screen, but the only way to solve it is to figure out when to fold/unfold it to create bridges and new routes. Along the way you’ll encounter increasing complex levels: cats and foxes patrolling, doors you need to unlock, platforms you can toggle, and floors that crumble under you.

Some fun things I built/had to do that aren’t obvious:

- I built a web based level editor that runs the game’s rules engine compiled from Swift to wasm.

- Every level is validated by a solver that identifies shortest solutions, lints the board and identifies which “tricks” are required to solve it. This helped me a few times when designing levels where I would make a change but accidentally would introduce a shortcut.

- Figuring out how to translate the fold mechanic to non iPhone Duos was a cool challenge, I ended up adding a “virtual” on screen fold, which still doesn’t justice to the game.

- As much as I would love to have some data on how people play the game, it was super important to me that the game worked totally offline, not collecting any data.

It was so incredibly fun to build this, as you can expect I leaned heavily into agentic tools, which enabled me to move pretty fast. Every puzzled was however designed by hand, AIs are not good at “fun”, and from a game design perspective this was the most interesting part to me.

The whole game costs $4.99, all 69 levels (and already working on new worlds), no IAP ever.

Trailer: https://www.youtube.com/watch?v=w98lwzHgGWA

If you’ve got a duo (or not) I’d love to hear your feedback. And more than happy to answer anything about building/designing it!

Show HN: Orisuji, a maze you solve by folding your phone