A half-open foldable is a paint box: AltoPaint launched alongside iPhone Duo and hit Top Paid charts in 35 countries, but sold few copies

A New York Instagram engineer built a side-project painting app called "pocket paint tin" in his spare time. It launched the same day as Apple's first foldable iPhone, the Duo, and the tin's lid lines up exactly with the phone's fold. It made Apple's Duo featured list and, within two weeks, showed up on Top Paid charts in 35 countries. Yet only 4 people in the whole world had rated it. This piece covers how it rode the wave, why you've already missed this one, and how to get ready for the next one.

An app that launched on the same day as the new phone

On Oct 23, 2026, the iPhone Duo went on sale. That same day, Eric Kunz posted on Threads that AltoPaint was live, and the post got about 580 likes. By day he is an Instagram engineer; by night he makes small apps through his one-person company, High Line Labs. The press release was written two days earlier and dated Oct 21. Its first line: "AltoPaint turns your phone into a tin of paints." It came with ten feature screenshots, each demoing one effect, plus a media kit download and a press contact email.

On launch day, the Apple news site iThinkDifferent ran a feature piece. On Nov 1, Kunz posted on Threads that the app had been featured by the App Store, and Instagram head Adam Mosseri replied underneath: "that's rad, congrats!"

What it is

The first line of the store page reads: "Curiously small paintings, in a paint tin that fits in your pocket."

• On opening, you see a paint tin: the top half shows a small canvas inside the lid, and the bottom half holds 12 paints and a palette.
• Paints mix the way real paints do: lemon yellow plus phthalo blue gives green, not the gray-green you'd get from averaging RGB. Each brush dip dries out as you paint, leaving dry-brush streaks. Wet paint gets dragged by your next stroke; dried paint doesn't. Paint laid on thick shows brush-hair grooves and sheen.
• Few tools: a flat brush, a palette knife, and a rag. Materials start with oil and gouache, and the Nov 6 1.1 update added watercolor.
• There is no undo. The store page gives this its own section: "Like real paint. Paint over it, scrape it off with the knife, or let it dry and paint on top. Nothing gets destroyed; it just becomes part of the painting."
• $4.99 launch week price, then $5.99 one-time purchase. No subscriptions, no in-app purchases, no ads.

The Duo-specific bit: the paint tin opens exactly along the screen's center line, which is where the Duo folds. Lay the Duo half-open on a table and the top half stands up like a lifted tin lid, with paints and palette lying flat on the bottom half. It also works on regular iPhones and iPads, just with the tin filling the whole screen.

Both US store reviews are 5 stars. One says "A unique painting app, fun and easy to pick up, lets you enjoy painting a simple little picture" (10-23). The other says "Cute and fun, very relaxing. I wish there was an undo, but as Bob Ross said, there are no mistakes, just happy accidents" (10-30).

How it charted: a new phone, an Apple feature, and a low-bar category

Checking which countries it showed up in on the App Store charts, day by day:

Three things stacked together:

1. New phones lack apps worth showing off. When a new form-factor phone goes on sale, early buyers look for things only that phone can do, and media want "must-have Duo apps" lists. Apple opened Duo compatibility submissions on Oct 5, and AltoPaint went live on launch day.

2. An Apple editor put it in a feature. It sat alongside Halide, Penbook, Deck-Man, and TypeDraw in "Great Apps and Games on iPhone Duo." In the two days after the feature went up, the number of countries it charted in jumped from 16 to 27, matching the timing. On Nov 3, iThinkDifferent wrote "iPhone Duo Brings Back Skeuomorphic Design," listing it with the toaster game Toastie, the cassette player Deck-Man, and the instant camera pico cam as must-have Duo apps. The "fold is the lid" hook explains itself in one image, which made it easy for editors and media to use.

3. The paid category bar is low. The #1 spot on the Graphics & Design Top Paid chart was Procreate Pocket (#13 on the US Top Paid overall chart), and the chart thins out fast below that. A $5 one-time app selling a few copies a day can land in the top 5 of that category in many countries. Across 35 countries, it mostly ranked between #2 and #4 in the category.

Searching TikTok turns up no videos about it, X hasn't discussed it in the past month, Reddit has no dedicated threads, and mainstream tech outlets (MacRumors, Wired, Tom's Guide) left it off their Duo lists. All the traffic came from Apple's featured slots and small Apple-focused media.

How much it actually sold: not much

In two weeks of being live, it had 4 ratings worldwide, 3 of them in the US. The number of countries it charted in grew from 8 to 35, while ratings grew by only 3. Paid apps typically see only one or two of every 100 buyers leave a rating, so the estimate is a few hundred to about two or three thousand sales, roughly $ several thousand to just over $10K in revenue (estimate). The author has never published figures.

The comparison says a lot:

• The same author launched Hinge Harp the next day (10-24), a pocket instrument also designed around the Duo fold. It was not featured by Apple and only ranked between #22 and #102 in the category charts of 1 countries. Saying "built for the Duo" isn't enough; the featured slot is what matters.
• Among the Duo launch apps, the cassette player Deck-Man had a demo video with over 200 million views before release, and a blogger used it for an unboxing that pushed it to the top 20 of the US Top Paid overall chart. AltoPaint had no such spread and stalled around #100.

Who it's competing with

Among painting apps, it is very small:

Technically there's no moat. Spectral color mixing already has ready-made libraries you can license (such as Mixbox), so matching the same mixing effect isn't hard. Its real differences are two things: deliberate smallness (small canvas, 12 colors, no undo) and the "fold as tin lid" form. The first is positioning, which anyone can copy. The second caught the launch window, and that window has already closed.

What it really competes with isn't other painting apps but the rest of the Duo launch apps: toaster games, cassette players, retro computers, leather wallets, notebooks. They're all fighting over the same featured list and the same "must-have" roundups.

If it were you

C: worth learning from, not worth copying now. The Duo launch featured slots are already distributed, and even a feature only brings a few hundred to a few thousand one-time purchases. The approach is worth studying for the next hardware launch.

Who it suits: iOS indie devs who can build refined native interactions, who are willing to bet on one or two "new hardware launches" a year and don't expect a single app to support them, and who find craft, skeuomorphism, and small toys more satisfying than growth work.

Who it doesn't suit: anyone who wants steady income. It's a one-time purchase with no subscription, sales fall once the feature ends, and there's no repeat purchase. Building "another realistic painting app" is also a bad fit: Procreate, Fresco, and Art Set already own that space, and realistic color mixing isn't proprietary tech.

How to do it:

• Watch launch dates for the next "new form-factor hardware": a new foldable, new sensors, new input methods. Start the day Apple opens compatibility submissions, and be live on launch day.
• Build one idea that only makes sense on that device, ideally one a single screenshot can explain, like "the fold is the lid." Apple editors and media both need examples they can illustrate.
• Turn the limitation into the selling point. "No undo" was a weakness; once written as "like real paint," users in reviews defended it for it.
• If you still want to build for the Duo: find something no one has done on the Duo yet that can be shown in a three-second video. Deck-Man beat AltoPaint because of video, not product.

How to get users: Two days before launch, write the press release and prepare a media kit with a screenshot for each feature. On launch day, send it straight to Apple-focused press (iThinkDifferent, iPhone in Canada, 9to5Mac tier). Also shoot a vertical demo video and get unboxing creators to film it. One to two weeks after launch, rewrite the title based on search terms: when AltoPaint 1.1 added watercolor, the title changed from "Oil & Gouache" to "Oil & Watercolor", since watercolor gets far more searches than gouache.

How early is early: the Duo featured slots will most likely rotate out around the end of the year (inference). What you can do now is prepare an app for the next new form-factor hardware and submit the moment compatibility opens.

What would show you misread this: (1) after the feature was removed, AltoPaint, renamed and with watercolor added, held the top 150 on the US Top Paid overall chart through "watercolor" searches alone, which would mean "small realistic painting toys" have organic demand and are worth a different platform or language; (2) Duo sales far beyond expectations, with third-party roundups still pushing it, so the window lasts longer than expected; (3) the author publicly reporting sales well above a few thousand.

Data and sources: App Store charts and ratings (10-28 to 11-06, about 35 countries); App Store store page and 1.1 release notes (11-06); App Store feature "Great Apps and Games on iPhone Duo"; the altopaint.app/press press release (10-21); iThinkDifferent's 10-23 feature and its 11-03 article "iPhone Duo Apps Bring Back Skeuomorphic Design"; Eric Kunz's Threads posts (10-23, 11-01). Sales and revenue are estimated from rating counts; the author has not published them.