Beta release. Problem Forge is new and open by invitation. The beta test period runs through 2026-11-30; the full opening is on 2026-12-01 00:00 UTC. Things may break, and we may correct the boards when they do. The difficulty of some rungs may be wrong. There are no prizes during the beta, and the bounty is not open. Your account and your progress stay when the beta ends. Please tell us what goes well and what goes wrong: admin@problemforge.com.

Start here

Think of this as a contest. Solve as many of the 12 instances from the Problem of the Month (and from the repeated set of 10 challenges) as possible. Keep checking your place on the leaderboard.

  1. Pick a problem. Each problem page explains the problem. The instances change every month. More importantly, the instances for each challenge (those offered here and now) increase in difficulty.
  2. Try a sample. The samples need no account. Each comes with its answer.
  3. Sign in to compete. Use Google, GitHub or a code sent to your e-mail address.
  4. Plan your approach. The very first rung does not count toward your score. Use it to learn how the instances are encoded and how to send an answer. There is an API so you don't have to cut-n-paste material into the web page.
  5. Compete. The monthly leaderboard is one aspect of measuring your progress. You can also check your solutions before you send them. Use the Check page, or download the checker and run it on your computer.
  6. Be flexible. For each problem, there's only one rung allowed open at a time. You must solve the open rung to reach the next. The difficulty increases with each step upward. So, ... What got you past the previous rungs might not be good enough for the next.

Help and reading

Competing

Your personal clock for each instance starts when you open it for the first time that month; it stops when you submit a correct solution. All the instances from the Problem of the Month and the ten repeated challenges are counted equally; however, as a caution, they're not equally difficult.

You score one point for submitting a correct solution and the time elapsed (on your personal clock for that instance) will add to your total time. As far as the leaderboards go, on equal points, less total time will rank higher. That implies that your strategy for deciding which instances to tackle next (and when to open them) might matter. Some of the leaderboards and all of the problem instances reset each month on the first. The first Problem of the Month, for December, is available now; it will change in January and every month after that. All bounty problems will persist until solved. Other planned changes will reflect trying to make the ten repeating problems more entertaining (and they might rotate in various ways to confuse the unwary).

Recommended goal: Improving your score from month to month (and dramatically over the long run).