A cairn is the stack of rocks that marks the trail and tells you other travelers came this way. Every Dark Rock Studios app carries one; it points to the rest of the family.

Cairn is the shared "About" screen for Dark Rock Studios apps, as a Compose Multiplatform library: the studio identity, the current app, the family of sibling apps, and support links — wearing the darkrockstudios.com design language. The survey grid glows under your finger, seams ignite as they scroll into view, the horizon foil gleams as you tilt the phone, and opening it etches the grid over your app's screen before the basalt floods in.

You almost certainly don't want this library. It exists for Dark Rock Studios applications: the app catalog, branding, and links are baked in. The code is Apache-2.0 and you're welcome to learn from or fork it for your own studio's about screen — but the Dark Rock Studios name, logo, and app icons are not openly licensed (see NOTICE).

• Targets: Android, iOS (arm64 + simulator), Desktop (JVM), WebAssembly
• Zero third-party dependencies, zero permissions, zero network requests
• Design spec and interaction prototype live in the AboutDarkrock workspace

dependencies {
    implementation("com.darkrockstudios:cairn:<version>")
}

Overlay presentation (recommended — the entrance plays over your app's own screen). Place it as the last child of a full-screen container:

var aboutVisible by remember { mutableStateOf(false) }

Box(Modifier.fillMaxSize()) {
    MyAppContent(onAboutClick = { aboutVisible = true })

    CairnAboutOverlay(
        visible = aboutVisible,
        config = CairnConfig(
            currentAppId = CairnAppId.FastTrack,   // YOUR app
            versionName = BuildConfig.VERSION_NAME,
        ),
        onDismissed = { aboutVisible = false },
    )
}

Or as a standalone destination: CairnAboutScreen(config, onClose = { ... }).

• Back handling: while the overlay is visible it intercepts system back and plays the exit ceremony, then calls onDismissed.
• Installed detection (Android): the library AAR ships the <queries> entries; your app inherits them via manifest merge. Nothing to add.
• Installed detection (iOS): add the family URL schemes to LSApplicationQueriesSchemes in your Info.plist if/when catalog apps declare schemes; without it detection degrades gracefully to "not installed".
• Store routing: GET buttons link to the store this install came from (Play/F-Droid detected at runtime; Aurora and sideloads route to the app's canonical page). Rate only appears on Play/App Store installs. Share only appears where a platform share sheet exists.
• Audio: sonification-class output — never requests audio focus, never ducks the user's media, respects silent-switch contexts. Users can mute from the screen's footer (persisted).
• Sensors: accelerometer only, permissionless on both platforms, sampled ~30Hz strictly while the screen is visible.

./gradlew :sampleApp:run                      # desktop sample (fake Fast Track host)
./gradlew :sampleApp:wasmJsBrowserDevelopmentRun   # browser sample
./gradlew :androidApp:installDebug            # Android sample
./gradlew :cairn:desktopTest                  # tests + render previews (build/preview/*.png)
./gradlew :sampleApp:updateDemo               # rebuild the GitHub Pages demo in docs/

In the desktop sample: arrow keys simulate device tilt (R resets), mouse hover drives the flashlight/gleam/sheen, and the render-preview tests write deterministic PNGs of every effect for visual regression.

The app catalog is hand-written in CairnCatalog.kt for now, with field names mirroring the website's project frontmatter so a website→Kotlin generator can replace it mechanically.

Code: Apache-2.0. Brand assets (Dark Rock Studios name, summit logo, app icons): not openly licensed — see NOTICE. Bundled fonts: OFL-1.1 — see NOTICE-FONTS.md.