Last updated 11 October 2026. Ceteris is run by Luke Masom, a sole trader trading as Ceteris, contact hello@ceteris.app. The full trader details, and your rights if you buy something, are on the terms page.
The short version: you can play every game here without giving us anything, and that is not going to change. An account is offered for one reason — so a streak survives a cleared browser and follows you to another device — and it asks for an email address and nothing else. We do not use Google Analytics, Facebook pixels, advertising tags, or any third-party tracker. The only cookies we set are one random analytics identifier on our own domain, which you can switch off, and one that keeps the membership prices you are shown the same on each visit, both described below. Nothing about you is sold or shared with anyone.
Your guesses, your streak, your badges, the countries you have named on the world map, your XP and rank, and whether you have hard mode on are all stored in your browser’s local storage. If you do not have an account, that is the only copy. Clearing your browser data erases it, and a phone and a laptop are two separate streaks — we cannot see either of them and cannot restore them.
An account exists to fix exactly that, and nothing else. It is described in the next section, it is optional, and every game is fully playable without one.
a41e0c77b93d. It means nothing outside this system.That is the complete list. No name, no date of birth, no location, no phone number, no password. There is no password because there is no password field: you sign in by clicking a link we email you, which expires in 20 minutes and works once, or by choosing Sign in with Google. Your IP address is never written to your account record — see the next section for the one place it is touched at all.
Lawful basis: consent (UK GDPR Article 6(1)(a)), given by asking for a sign-in link or choosing Sign in with Google, and withdrawable at any time by deleting the account. Nothing about an account is required to play, and no feature is withheld from people without one.
The newsletter is a separate, unticked box. Leaving an account does not subscribe you to anything, and subscribing does not require an account. If you tick it, your address joins the Everything Econ mailing list described below; you can untick it on your profile at any time, and every email carries a one-click unsubscribe.
Sign-in emails are a way to bother a stranger, so we limit how many can be sent to one address or from one connection in an hour. That limit is the only thing that touches your IP address. It is stored as a one-way hash — a scrambled fingerprint that cannot be turned back into an address — alongside a timestamp, and the entry is deleted within an hour. It is never written to your account, never joined to your progress, and never used for analytics.
When you open the game, finish a puzzle, or tap a link, the page sends a short line to our own server (no third party is involved). Each line contains:
k3f9x2mq, which lets us count returning players without knowing who they are;9c41e07ab2d35f18, which our server keeps in a cookie called cet_cid on ceteris.app for up to 400 days. Browsers clear the first identifier more often than a cookie, so without this second one a returning player is often counted as new. It is used only for the same counts, it is never shared, and it is never linked to an email address or an account;instagram.com), never the full address.We do not store your IP address, your name, your location, your device model, or your browsing history. The random identifier is not linked to anything that identifies you, and it disappears if you clear your browser data.
We use this only for statistics that tell us how to improve the site: how many people play, how many come back, how many finish, which links bring people who stay. Lawful basis: legitimate interests (UK GDPR Article 6(1)(f)) in understanding whether the site is working. Storing the identifiers on your device relies on the statistical-purposes exemption in regulation 6 of the Privacy and Electronic Communications Regulations, which requires us to tell you and to let you object.
Switch analytics off. Turn off analytics in this browser. This sets a cookie called cet_noan that tells our server to discard everything this browser sends, and deletes the cet_cid cookie. It lasts 400 days or until you clear your cookies. Turn analytics back on.
Membership prices. We are testing two annual prices. The first time you see the membership plans, our server picks one of them at random and stores which in a cookie called cet_px on ceteris.app for up to 400 days, with a random identifier, so you see the same prices every time; if you have an account, the same choice is saved to it. Prices are shown in pounds, US dollars or euros depending on the country your connection comes from, which our server looks up from your IP address each time and does not store. We record which prices were shown and whether a purchase followed, to compare the two prices. Lawful basis: legitimate interests in setting our prices.
Feedback you send. If you rate a game or a module, or answer “What should we build next?”, we store your answer, any comment you type, the page, the game or module, and the same random identifier, so we can count answers without counting one person twice. Please do not put personal details in a comment. Lawful basis: legitimate interests in improving the site. We delete feedback after 24 months.
An address you give the newsletter is stored on our server against the date you signed up and the day number you were on. Lawful basis: consent (UK GDPR Article 6(1)(a)), given by submitting the form, and withdrawable at any time. Every email we send will carry a one-click unsubscribe link. We use it for nothing other than the Ceteris email and occasional news about Everything Econ products.
Who processes it. Your address is also sent to beehiiv, the email service we use to send the newsletter, which processes it on our behalf. beehiiv is told your address and that you signed up through Ceteris (the game or the Learn page), and nothing else about you. Unsubscribe from any email and beehiiv stops sending; write to us and we will delete the address from our server and from beehiiv.
The card at the end of a game has two separate boxes, both unticked. Tick neither and nothing is signed up. Whatever you tick, we first email you a link to confirm, and nothing else is sent until you click it. For each box we keep the exact wording you saw, the time you ticked it, the time you confirmed and, if you stop, the time you stopped, so we can show what you agreed to. Lawful basis: consent (UK GDPR Article 6(1)(a)), withdrawable at any time.
“A weekly email: one headline and the story behind it” is the Everything Econ newsletter. Once you confirm, your address goes to beehiiv as described above. Each issue has its own unsubscribe link.
“Email me something worth reading when I haven’t been back for a while” is a Ceteris email with a fact, a module to try next and the latest modules. To decide when to send one and what to suggest, your browser tells our server, at most once a day, which days you finished a Learn module, which modules you have finished, the last module you opened and your answer to “What are you studying?”. If you are signed in we also read the Learn progress already stored with your account. We send nothing to anyone who has been back in the last two days or has finished a module today or yesterday, nothing after 9pm, and we stop after three emails you have not opened a link in. If you are studying for A-level, GCSE or IB, or have not told us, these emails never mention streaks and come at most once a week. Adults with an account may get one email the morning after a streak of three days or more ends, with a link that adds the missed day back once a month. To see whether these emails help, we keep the days you visit for 60 days and which link in an email you opened, and we may send two versions of an email, each reader getting one version at random. Every one of these emails has a link that stops them in one tap. They are sent from hello@ceteris.app, through Hostinger.
An address that is never confirmed is deleted after 30 days. Once you stop every email you signed up for, the record of what you agreed to and when is kept for two years, so we can show it if asked, and then deleted. Ask us and we delete it sooner.
Who else handles data. Hostinger hosts this website and the hello@ceteris.app mailbox, and the order confirmations and sign-in links we send you leave from that mailbox, so Hostinger handles those messages. Stripe handles payment, described below. Google is involved only if you choose Sign in with Google on the profile page. That page loads Google’s sign-in code, and only when you are signed out, so Google sees that the page was opened, along with your IP address and browser details, under its own privacy policy. When you use the button, Google tells us your email address if it has verified it. We keep that address as your account, the same as if you had typed it in, and we keep nothing else from Google (not your name, picture or Google ID). No other page loads anything from Google. We do not use advertising or analytics services from anyone else, and apart from that one sign-in script no third-party script runs on these pages.
Most of Ceteris needs none of this. If you do buy a subscription, three more things happen, and nothing else changes.
Payment is taken by Stripe, who process it on our behalf under their own terms. We never see, receive or store your card number. If you cancel, you do that on Stripe’s own pages, reached from a button on your profile.
What we store, on your account record and nowhere else:
Lawful basis: contract (UK GDPR Article 6(1)(b)). We need this to give you the thing you paid for and to stop charging you when you cancel. It is not consent, and it is not something you can be asked to agree to separately — without it there is no purchase.
We also email you an order confirmation. That is not marketing and you cannot unsubscribe from it: the law requires us to confirm your order in writing, and it is also the record you would use to ask for a refund.
One honest detail about deletion. A purchase record is added to, never overwritten — a refund marks the old entry refunded rather than erasing it, so the history of what happened to your money stays intact. All of it is still attached to your account, so deleting your account deletes it, exactly as described below. Stripe keeps its own payment records for as long as UK tax and anti-fraud law requires, which is not something we control or can delete for you.
Who can buy. If you are under 18, you need permission from a parent or guardian to buy. We do not ask your age before showing prices and we do not record it.
An admissions pass stores a little more, on our own server and attached to your account:
Admissions payments are taken by Stripe on the EconCoaching account (EconCoaching and Ceteris are both run by Luke Masom). Stripe gives us your email address, the plan and the amount; we never see your card details.
Lawful basis: contract (UK GDPR Article 6(1)(b)). These are the features you bought. Deleting your account deletes all of it except an issued certificate’s record, which you can ask us to remove.
A lot of our audience is studying A-level or IB Economics, so this matters. You can play every game freely at any age, with no account and no email address. If you are under 13, please do not create an account or submit your email address without a parent or guardian’s permission. If you are a parent and would like an address removed, email us and we will delete it — no questions and no proof required.
Nothing here is sold to you. Every daily puzzle, the games and some Learn modules are open at any age, with no subscription. We never sell a way to repair a streak, buy a life back, or carry on after a mistake, and we are not going to start. If a payment was made by someone under 18, or on your card without you knowing, email us and we will refund it — we will not ask you to prove it.
Open your profile, scroll to Your account, and tap Delete my account and data. It asks once more, then deletes immediately: your email address, your random id, your stored progress and every sign-in session are removed from our server there and then. There is no queue, no 30-day window and no need to email anybody.
Deleting the account does not touch the copy in your own browser, so your streak carries on locally afterwards. If you want that gone too, clear your browsing data for this site.
If you would rather we did it, or you can no longer sign in, email contact@econcoaching.com from the address you used, or naming it, and we will delete it within 30 days — usually the same week. You can also ask for a copy of what we hold, ask us to correct it, or object to the analytics described above. Because the play data carries no identifier we can tie to you, we may not be able to find your specific rows in it, but you can erase your own copy by clearing your browser data.
If you are not happy with how we have handled a request, you can complain to the Information Commissioner’s Office at ico.org.uk.
Play records are kept for 24 months and then deleted.
Accounts are deleted after 24 months of inactivity. If you do not sign in or play for two years, the whole record — email address, random id and progress — is deleted automatically. This is not a promise we keep by remembering to do it: it is a rule in the code that runs on the server as part of ordinary traffic, and it deletes the account without anyone being asked. The clock resets every time you play or sign in.
Sign-in links expire after 20 minutes and can be used once. A signed-in session lasts up to 400 days and is refreshed each time you use it. Newsletter addresses are kept until you unsubscribe or ask us to remove them.
The game links out to articles, posters, and the newsletter on econcoaching.com and to related shops. Once you follow one of those links you are on that site and its own privacy terms apply. Where the link carries a tag telling us the visit came from the game, that tag identifies the puzzle, not you.