Privacy policy

Stillstone for Android · Last updated October 11, 2026

Who is responsible

Stillstone is a mahjong solitaire game for Android (package com.hundredships.stillstone) made by ZK Lab, which is responsible for this app and this website. For anything about this policy or your data, write to zklab@hundredships.com.

What the app keeps on your phone

To work offline, the app keeps these in its private storage on your phone:

• your settings, such as tile size, tile set, board background, sound, vibration and the reminder time;
• your progress: solved levels and daily boards with their times, your streak, records for each layout, and a list of solved boards (date, kind of board, layout, time, and whether you used help);
• boards you haven't finished, so you can continue them;
• 24-hour unlocks and theme trials, and how often the app has asked you for a review;
• what you have bought, so Plus and “Remove ads” work without a connection;
• counters that space out ads, such as how many boards you solved since the last one.

None of this is sent to us. If backup is on in your phone's settings, Android may include your settings, progress, unlocks and unfinished boards in the backup of your Google account, so they come back on a new phone. That backup is run by Google and Android; it leaves out your purchases and the ad counters.

Advertising

The free version shows ads from Google AdMob: a banner on some screens (never on the board), an ad now and then when you leave the results of a solved board, and rewarded ads only when you choose to watch one for extra help or a 24-hour unlock. Ads are limited to content rated PG.

Before any ad is requested, Google's consent tool (the User Messaging Platform) checks with Google whether a consent form is needed where you are. To show ads, measure them and prevent fraud, Google's Mobile Ads SDK then collects and sends to Google:

• your IP address, which can show your approximate location;
• how you interact with ads and the app, such as ads seen and tapped and app launches;
• diagnostic information about the SDK and how it performs, such as crash logs and load times;
• device or other identifiers, such as your phone's advertising ID and app set ID.

This data is shared with Google for advertising and marketing, analytics, and fraud prevention, security and compliance. It is encrypted in transit. Google is responsible for it as a separate controller and uses it as described in How Google uses information from sites or apps that use its services. With Stillstone Plus or the one-time “Remove ads” purchase, the app doesn't start the consent tool or the ads SDK and requests no ads.

Your choices for ads

In the European Economic Area, the United Kingdom and Switzerland, the app asks for your consent through Google's consent form before it requests ads. If you don't consent, Google may still show limited ads that aren't personalised. You can change or withdraw your choice at any time under Settings → Privacy options in the app.

You can reset or delete your advertising ID in your phone's settings, usually under Settings → Privacy → Ads or Settings → Google → Ads.

Purchases

Stillstone Plus (a subscription) and “Remove ads” (a one-time purchase) are sold through Google Play. We don't receive your payment details: Google Play tells the app only what you own and whether a payment is still pending, and the app keeps that on your phone. Subscriptions are managed and cancelled in Google Play. Google's privacy policy applies to the purchase itself.

Reviews and notifications

Now and then the app may ask Google Play to show its review form. What you write goes to Google Play; we only see it as a public review there.

The daily reminder and the notice the day before a free trial ends are planned on your phone and shown only if you allow notifications. No server sends them.

Crash and performance reports

The app has no analytics or crash-reporting service of its own. If you let your phone share usage and diagnostics data with Google, Google Play may show us summarised crash and performance statistics that don't identify you.

This website

This website is hosted by Railway (Railway Corporation, USA). When you open a page, Railway processes your IP address, the page requested, the time and your browser's details to deliver the page and keep the service secure, and may log them for a short time. The website sets no cookies, uses no tracking or analytics, and loads no fonts or scripts from anyone else.

Legal bases (EEA, UK and Switzerland)

• Personalised ads and the use of your advertising ID and other device information for ads: your consent (Art. 6(1)(a) GDPR), which you can withdraw at any time under Settings → Privacy options.
• Limited, non-personalised ads, the consent check, ad measurement and fraud prevention: our legitimate interest in funding the free version and keeping ads safe (Art. 6(1)(f) GDPR).
• Purchases and restoring them: performing the contract with you (Art. 6(1)(b) GDPR).
• Delivering this website: our legitimate interest in a secure, working website (Art. 6(1)(f) GDPR).

Transfers outside Europe

Google and Railway may process data in the United States and other countries. Google LLC is certified under the EU-U.S. Data Privacy Framework (with its UK extension and the Swiss-U.S. framework). Railway relies on the European Commission's standard contractual clauses in its data processing terms.

How long data is kept

What the app keeps stays on your phone until you delete it (see below). Google keeps the data it collects for ads as described in How Google retains data. Railway's request logs are kept only briefly.

Deleting your data

Everything the app keeps is on your phone. To delete it, clear the app's storage (Settings → Apps → Stillstone → Storage → Clear storage) or uninstall the app. We keep no copy, so there is nothing to ask us to delete. Your Google account's backup and the data Google holds for ads are managed in your Google account.

Your rights

Under data protection law you have the right to access your personal data and to have it corrected, deleted or restricted, the right to data portability, the right to object to processing based on legitimate interests, and the right to withdraw consent at any time without affecting what happened before. Because we don't receive or store personal data about you, we have none to show you, correct or delete. Google is responsible for the data it collects for ads and purchases; see Google's privacy policy. You can write to us with any question, and you have the right to complain to a data protection authority, for example the one where you live.

Adults only

Stillstone is made for adults aged 18 and over and isn't directed at children.

Changes

If the app's handling of data changes, we update this page and the date at the top.