R3CK0N
The daily mental math challenge is 20 arithmetic problems, the same for every player in the world, free to play in your browser with no signup, and new every day at midnight UTC.
You get one attempt. Finish it and you see how many you got right, your pace in correct answers per minute, your total time, and a share grid in the style of Wordle that you can paste anywhere. Sign in and your score goes on the day's board with a rank. Stay signed out and you still play the exact same set; you just cannot post it.
The same problems for everyone. The set is generated from the date rather than downloaded, so a player with no account, or no connection, faces the identical 20 problems in the identical order. That is what makes the results comparable: two players who both score 18 of 20 can argue about pace, because they solved the same things.
What is in it. An even blend of addition, subtraction, multiplication and division at the Medium level of Math mode: sums and differences with numbers up to 999, multiplication of two numbers up to 99, and division by up to 12 with whole-number answers up to 50. No tricks and no decimals. It is a speed test of ordinary arithmetic, which is why it works as a daily habit.
One attempt a day. The challenge turns over at 00:00 UTC, the same instant everywhere, so "today" means the same day in Auckland and Los Angeles. Each challenge is numbered (the first was 1 September 2026) and the number is what the share text carries. After your attempt you can replay the day's problems as practice as often as you like. Replays count in your stats but never touch the board.
How it is scored. Correct out of 20, and pace in ppm: correct answers divided by the minutes you spent answering. The day's board ranks by most correct first and fastest total time second, so a careful 20 beats a hasty 19 however quick it was.
Problem 7 is 612 − 287. Round 287 up to 300: 612 − 300 = 312, then add the 13 back: 325. Problem 12 is 432 ÷ 12: twelve 36s are 432, so 36. Type each answer and the next problem appears at once.
Say you finish with 18 right out of 20 in 1 minute 40 seconds of answering time. Pace is 18 divided by 1.67 minutes, about 11 ppm. The share text reads "R3CK0N #66 — 18/20 · 11 ppm" over two rows of ten squares, two of them red, with a link back to this page so a friend can try the same set.
It is free and you can play without an account; the problems are the same whether or not you are signed in. Signing in is only needed to post your score to the day's board and see your rank.
At midnight UTC, the same moment for everyone: 7 or 8 pm in New York depending on daylight saving, and 9 am in Tokyo. A tab left open through the rollover notices and offers the new day.
Each day's challenge takes one attempt, and that is the score that counts. After it you can replay the same problems as practice, which is saved in your stats but kept off the board.
All 20 right comes first, because the board ranks by correct answers before time. For pace, the Medium speed tiers used in Math mode put 10 ppm at Quick, 15 at Sharp and 22 at Lightning. The board itself tells you where that lands on the day.
JavaScript is needed to play.