Draft, for counsel review. These terms are not final. A lawyer will review them.

Terms of use

Version draft-2026-10-25.

These terms are the agreement between you and Problem Forge about the site. Please read them before you create an account. The rules give the details of the contest. If these terms and another page on the site disagree, these terms win. The one exception is a bounty: its own terms govern it.

Who we are

The site is run by Problem Forge, LLC, a Washington limited liability company, in the United States. In these terms, "Problem Forge", "we" and "us" mean Problem Forge, LLC. "The site" means problemforge.com and everything it offers, including the API and the checker. "You" means the person using the site.

You can write to us at admin@problemforge.com.

Agreeing to these terms

You can read the public pages without agreeing to anything.
To create an account, you must tick the box that says you have read these terms and the privacy notice. Ticking it is your agreement to these terms.
If you do not agree, do not create an account. If you already have one, you can erase it at any time in Settings.

What the site is

The site is a game. Each month it offers new ladders of hard problems. It is for fun and for learning. It is not a test, a job offer or a service with any promised result.

The beta

The beta runs through 2026-11-30. The site opens fully on 2026-12-01 at 00:00 UTC. During the beta:

Things may break. Pages, files and the checker may change.
We may correct or reset leaderboards and statistics when a bug has changed them. We will say so on the site.
The difficulty of some rungs may be wrong.
There are no prizes during the beta. No bounty is open: you can look at a bounty's instance, but answers cannot be sent.
You need an invite code to sign up. A code is for one person.
Your account and your progress stay when the beta ends, unless we tell you otherwise on the site before it ends.
These terms may change when the beta ends. If the change matters, we will ask you to tick the box again.

Guests

You can read every page without an account.
Guests can try the samples on each problem's page. Each sample comes with its answer.
Guests get no cookie. We keep no record of their visits; see the privacy notice.
Guests cannot climb, send answers to us, appear on a leaderboard, or claim a bounty.

Your account

To climb, you sign in with Google or GitHub, or with a code we send to your e-mail address.
The first time, you must tick a box. It says you have read these terms and the privacy notice. Without the tick, no account is made.
We record when you ticked the box and which version of the terms it was.
From Google or GitHub we keep only an id that says it is you. We never ask them for your name, e-mail or profile.
If you sign in with an e-mail address, we keep only a fingerprint of the address (a keyed hash), not the address itself. Our mail provider sees the address in order to deliver the code.
We ask for an e-mail address in one other case: to send you a link to an old copy that takes a while to prepare (see The month). That address is optional and is not saved.
During the beta, a new account needs an invite code. Each code works once. An account can make up to ten codes.
We give invite codes to people one by one, and we say in public places that they are available. Give your invite code only to people you trust. We may stop a code that is posted in public.

You can link more than one sign-in method to your account, but only one per provider.
You cannot link a sign-in that already belongs to another account. We never merge accounts.
You cannot remove your last sign-in method. To leave, erase your account.
To link or remove a method, you must have signed in within the last 15 minutes.
A session lasts at most 30 days. It ends after 14 days without use. You can sign out everywhere in Settings.
The sign-in providers have their own rules, including minimum ages. Those rules still apply to you.
We limit how many new accounts one network can make in an hour. An existing account can always sign in.
Please keep to one account per person. This is a request, not a rule.
If an account is used to abuse the site (for example to attack it, get around its limits, or do something illegal), we may revoke its API tokens, end its sessions or suspend it. A suspended account cannot sign in; write to admin@problemforge.com. See also What you may not do.

Age

We do not ask your age, and we set no age limit of our own.
The sign-in providers set their own minimum ages, and those still apply to you.
The site is not directed at children. We do not knowingly keep data about a child under 13. If you tell us at admin@problemforge.com that a child under 13 has an account, we will erase it.

Your climber number

Each account gets a private 20-digit climber number.
Only you see it, on your own pages and in your own file names.
Give it to us if you write to us for help. Nobody else needs it.
It is not a password. Your sign-in and your API tokens prove who you are.

Handles

Your handle is the name others see on the leaderboards.
A new account starts with a handle like climber-k7q2m9xd4p.
A handle is 2 to 32 letters or digits. It may have spaces, dots, dashes or underscores between them.
Handles are not unique. If someone already uses yours, you get a number after it, such as "David (2)". Numbers are never reused.
Some handles are not allowed. Examples: words like "admin", "staff" or "support", the site's name, 20-digit numbers, and names of problems.
Your first change is free. After that, you can change your handle once every 30 days, and at most 3 times a year.
We may reset a handle that pretends to be us or someone else, or that harasses people. It then becomes climber-<your id>, and you cannot change it. You can appeal by writing to us.

What you may not do

We keep these rules to the ones we can enforce.

Do not try to break the site: no attacks, no probing for weaknesses, no overloading it. If you find a security problem, tell us (see Contact).
Do not get around the limits: one answer a minute, the number of new accounts from one network, the invite codes, the API limits.
Do not use a handle that pretends to be us or someone else, or that harasses people.
Do not put other people's personal details in your handle or in anything you send us.
Do not use the site for anything illegal.

If you break these rules, we may reset your handle, stop your invite codes, revoke your API tokens, end your sessions, suspend your account or close it. A suspended account is off every board and the Firsts while it is suspended. You can write to us at admin@problemforge.com.

The problems

There are 10 problems. Each has a ladder of 12 rungs that count toward your score, 01 to 12, and a practice rung, 00.
Rung 00 is practice. Use it to learn the file format and how to send an answer. It does not count toward your score.
You see the next rung only after you solve the one you are on.
Each rung you get is your own copy. Another climber's answer will not solve it.
Your answer is an integer. Its binary digits spell out the solution.
We reply to an answer with one of three words: accepted, not accepted, or malformed. For the ten problems we never say why; the Problem of the Month gives the reason. The checker on your own computer can tell you more.
The rules give every detail of the problems, the clock, the scoring and the boards.

One answer a minute

You can send one answer a minute for each copy. A copy is one rung of one problem in one month. Each bounty counts as one copy too.
The minute counts from your last answer to that copy, whatever the result was.
Two cases cost no minute: an answer that is refused before it is sent because it is not all digits, and an answer we could not check because our checker could not be reached. The second does not count.
After an answer, the answer box shows how long to wait. The API replies 429 with the number of seconds.
There is no daily limit; automatic limits against overload apply.
A wrong answer costs you only the wait.

The clock

The clock for a rung starts when you first download its file, on the website or through the API. That first download is your attempt.
Rung 00 opens when its copy is shown on its page; where it is not shown, your first answer to it opens it.
We may prepare your copy before you open it. The clock still starts only when you download it.
Downloading the same file again does not restart the clock or add an attempt.
The clock stops when we receive your first accepted answer. The time we receive it is what counts.
A rung page first shows a "Show this problem" button. Pressing it shows the rung's name and its download link. It does not start the clock.
A rung's time counts toward your score only when you solve it.
Rung 00 is timed for the statistics. It never counts toward your score.

Scoring and leaderboards

Your score for a month is the number of rungs from 01 to 12 that you solve in it, on the ten problems and on the Problem of the Month. More is better.
Ties go to the lower total time. If that is equal too, the earlier last scoring answer goes first, and after that whoever first had an accepted answer on that board (rung 00 counts here).
There is one monthly leaderboard for all 10 problems and the Problem of the Month. Each problem also has its own leaderboard. The all-time leaderboard adds up every month.
A leaderboard shows the top 100. When you are signed in, it also shows your own place.
You appear on a leaderboard once you have a point on it.
Leaderboards freeze when the month ends.
Statistics for each rung are kept without names. They combine all months.
Firsts record who solved a rung first, while it was still unsolved. Rung 00 has no First. Firsts are a separate record, not part of the ranking.
The boards are for fun and recognition. There are no prizes for places on any board. Monthly honours are a line on your public profile, nothing more.
Staff get no honours. From the 2026-11 month on, they are not on the boards and take no Firsts (see Staff and eligibility).
We may correct a board when a bug, an outage or a broken rule has changed it. We say so on the site. Our decision on a correction is final.

Problem of the Month

Each month has one extra problem with its own page. It has a practice rung 00 and twelve rungs that count. Its rules:

Each rung from 01 to 12 you solve scores one point, with its time, on its own board and on the monthly and all-time leaderboards of the month in which it runs, like a ladder rung.
You may download its rungs in any order. Each rung's clock starts at your first download of that rung, or when you first show its graph or key.
Its page names the ways around the contest that we know of, so that everyone knows them. Using a published method is the point, not a trick.
No answers are accepted after it closes. Its page stays readable.
A "preview" works the same way and is marked as a preview. It counts toward the month in which it is held.

The month

A new month starts at 00:00 UTC on the 1st. That is the same moment for everyone.
Progress does not carry over. Everyone starts again at rung 00.
Answers received before that moment count. Later ones do not.
When a month ends, you get, for each of the ten problems, the answer to your own copy of the rung that stopped you: the lowest rung you did not solve. Only you see it.
Your own past months stay on your pages. You can get your old copies again.
We do not keep old copies. We prepare yours again when you ask. You can ask for 3 old copies a day. Rungs 00 to 03 do not count.
Some old copies take a while to prepare. For those, we ask for an e-mail address. We send one e-mail with a link, then we delete the address. If our server restarts first, please ask again.
We publish no archive of past rungs.

Sharing and spoilers

Ideas, encodings, solvers and methods may be discussed anywhere at any time.
Please do not post answers, certificates or instance specifics of live puzzles until the first of the next month. After the reset, everything about that month is open.
After the month ends, you may post your own copy, your own answer and the answer we released to you.
Each copy is different, so a leaked answer does not solve another climber's copy. This is a request about fair play more than about the mechanics.
We may withdraw and replace a copy early if its answer is being shared in public. There is no other penalty.
Please keep answers to live puzzles out of a method page you write. After the reset, they may go in.

Discussion

The site has no forum, no chat and no public messages.
People discuss the problems on other sites, which we do not run.
We do not host, check or moderate those sites. Their own rules apply there.
Some of them are listed on the Discuss page.
Links to other sites are for your convenience. We do not control those sites and are not responsible for them. Their names belong to their owners.

Using AI and other help

You may use any tool, including AI assistants.
Please read On using AI for our view.

The API and the command line

You can make API tokens in Settings. Each token is shown only once.
A token lets a program climb for you. Keep it secret.
The one-answer-a-minute rule also applies to the API.
Programs may also fetch public pages at a reasonable rate.
Automatic limits protect the site from overload. Normal use never reaches them. A program that reaches them is slowed or blocked.

Staff and eligibility

We mark staff accounts. Staff may climb and see their own progress.
From the 2026-11 month on, staff do not appear on any leaderboard and take no Firsts. The First goes to the first solver who is not staff. The all-time board leaves staff out from 2026-11-01 00:00 UTC. In October 2026, staff appear on the boards with a "staff" mark.
Staff are not eligible for honours, badges, prizes or any bounty.
Guests have no account, so they are not eligible for anything.
A bounty's own terms may name others who are not eligible for it.

Bounty problems

There may be many bounty problems over time. Each has its own instance, its own prize and its own terms.
The current one, BOUNTY-SAT-0001, has a prize of US$1,000. Void where prohibited. The winner is responsible for any taxes, which may reduce the amount substantially.
You can look at its instance, but it is not open for answers yet. There are no prizes during the beta.
When a bounty opens, it will have its own terms. Those terms, not this page, will govern it. An outline is at /bounty/terms.
To claim a bounty, you will tick a separate box to confirm you have read its terms.
Bounty problems are outside the monthly score. One claim a minute is allowed for each bounty.
To post a bounty problem of your own, write to admin@problemforge.com.

Who owns what

The problem files and the answers we give out are dedicated to the public domain (CC0 1.0). You may use them for anything. We would still like a citation.
The checker is open source under the MIT licence.
Methods and write-ups stay yours.
See Licences for the full texts.

What you send us

On the site you send us answers, and you may choose a handle. We do not ask for your code, your methods or your write-ups.
You let us store your answers, check them and count them in the statistics. We never publish your answer while its month is live.
You let us store your handle and show it on the boards and on your profile. After you erase your account, your places show as "<anonymous>" instead.

Wiping and erasing

You can wipe your data or erase your account at any time, in Settings.
Both ask you to type a word to confirm. Both take effect at once and cannot be undone.
For both, you must have signed in within the last 15 minutes.
Wipe my data deletes your answers, times, handle and tokens, and signs you out everywhere. Your account stays. You can wipe once a day.
Erase my account deletes your account and everything tied to it. It leaves our backups within about five weeks.
After either one, your old leaderboard places and Firsts stay. They show as "<anonymous>", so other people's places do not change.
Counts without names, such as the statistics, stay.
Bounty claims stay for good, with the sign-ins that sent them, even after you erase your account. None can be sent yet.
If you sign in again after you erase your account, you get a new account and a new climber number.

Privacy

What we keep and why is in the privacy notice.

Our promises and their limits

Money never buys progress, a better rank, extra answers, hints or any advantage in a bounty.
We never keep a readable e-mail address. For sign-in by e-mail we keep only a keyed fingerprint of it (see the privacy notice).
We send no e-mail you did not ask for, we show no targeted advertising, and we never sell your data or share it for advertising.
We may change the problems, the rules or the site.

No warranty

The site, the files, the answers we release and the checker are provided "as is" and "as available".
We give no warranty of any kind, express or implied. This includes fitness for a particular purpose, accuracy, and that the site will be available or free of errors. The site may be down or wrong at times.
Some places do not allow this. There, it applies as far as the law allows.

Limit of liability

As far as the law allows, we are not liable to you for any indirect, incidental, special or consequential loss, or for lost data, lost time or lost profits, that arise from the site.
As far as the law allows, our total liability to you for anything that arises from the site is limited to US$100.
Nothing in these terms limits a liability that the law does not let us limit.

Suspension and ending

You can stop at any time: erase your account in Settings.
We may suspend or close an account as What you may not do says.
We may change, suspend or stop the site, a problem, a month or a feature at any time. If we stop the site, we will try to give notice on the site and leave Settings open long enough for you to erase your account.

Changes to these terms

Each version of these terms has a name, shown at the top.
We record which version you accepted.
If a change matters to you, we ask you to tick the box again. Small changes, such as clearer wording, do not need a new tick.
After such a change, the next page that needs your account shows what changed and the box. Until you tick it, you can still read the public pages, but you cannot climb or send answers.
If you do not accept the new terms, you can erase your account instead. That page has a link for this.

Law and disputes

These terms are governed by the law of the State of Washington, USA, without regard to its conflict-of-laws rules.
If we have a dispute, please write to us first. Most problems can be fixed by talking.
If that fails, the state and federal courts in Washington have exclusive jurisdiction, and you agree to that. Consumers in the European Union and the United Kingdom keep any right to bring a claim where they live.

The rest of the agreement

These terms, the rules, the privacy notice and the terms of any bounty you claim are the whole agreement between you and us about the site.
If a court finds part of these terms unenforceable, the rest stays in force.
We may transfer our rights and duties under these terms to a company that takes over the site. We will say so on the site, and ask you to tick the box again if the change matters.
The English text of these terms is the binding one. Translations are courtesy copies.

Contact

Contact: admin@problemforge.com

Legal notices go to the same address.
To report a security problem, write to the same address. We will not hold a good-faith report against you.
We read mail in English. A short note in another language is fine; we will do our best.