Last updated 28 August 2026. Applies to Puzzle Museum apps made by Millstone Studios — including Sudoku at the Museum, and future apps such as Painting at the Museum and The Puzzle Museum — on the platforms we release them on. Studio overview: millstonestudios.uk.
We don't create Millstone accounts, we don't show ads, and we don't use advertising or ad-tracking SDKs. Puzzle progress stays on your device and can sync across your Apple devices via your private iCloud account. Purchases stay with the App Store. We use Firebase for product analytics and crash reports, and our servers for catalog updates, downloads, and optional redeem codes. We don't sell your data.
We do not ask for your name, email address, or location, and we do not require a Millstone Studios account or sign-in to play. We do not run advertising networks or ad-tracking SDKs.
Puzzle progress, related preferences such as default difficulty, and hint balance are stored on your device. On Apple platforms they can sync across your devices through Apple's iCloud Key-Value Store when you are signed into iCloud with the same Apple ID. That sync is between your devices and Apple — Millstone Studios cannot read the contents of your iCloud account.
Purchase and entitlement status is not synced via iCloud. In-app purchases are tied to your App Store account. Use Restore Purchases in Settings (signed in with the same Apple ID used for the original purchase) to recover them on another device. Family Sharing, where enabled for a product, follows Apple's Family Sharing rules.
Our iOS apps use Google Firebase:
We use this information to understand what is working and to improve the apps. We do not use it to show you third-party ads. Firebase is operated by Google; see Google's privacy documentation for Firebase and Analytics for how Google processes this data.
We may receive anonymous or aggregated technical and sales data from the stores that distribute our apps — for example sales figures and anonymised crash statistics. We never see or store your payment card details. Purchases are processed entirely by the store (Apple App Store today; other stores if and when we expand). See that store's privacy policy for how it handles purchase data.
The apps contact Millstone Studios servers to check for content updates, fetch catalog and bundle metadata, and download pack content you are entitled to. Those requests identify the app and the content being requested; they are not a personal profile.
Optional redeem codes and operator grants use a random install identifier generated on your device (not your Apple ID). That identifier is stored with your progress (and can therefore sync via iCloud with progress) and is sent to our servers only when redeeming a code or checking server-side entitlements. We do not use it as a marketing identity.
Some apps offer optional in-app purchases — such as additional content bundles or unlimited hints. Where enabled, these support Family Sharing under Apple's rules. Purchases are tied to your app store account for delivery and restore purposes only.
Some apps may report achievements through Apple Game Center if you are already signed into Game Center. Game Center is optional and is not required to play. Apple's Game Center privacy terms apply to that service.
We do not knowingly collect names, emails, or other contact details from children. Our apps are not designed to solicit personal information from anyone. If you believe a child has provided contact information to us directly (for example by emailing support), contact us and we will delete it.
If a future version of an app needs to collect additional personal information, we will update this policy first, explain clearly what is collected and why, and — regardless of what the law requires — we will never sell or share that information with third parties for advertising or marketing purposes.
Questions about this policy can be sent to privacy@thepuzzlemuseum.app.