Septonum

Septonum is a mental arithmetic sprint served seven times a day. Each round hands you six numbers and a target somewhere between 101 and 999, and you combine the numbers with the four operations to land on it or get as near as you can. The clock gives you two minutes per calculation and it does not start until you press Start, which turns the waiting into part of the design. The working happens one operation at a time in a slot that reads as two numbers, an operator and a result, with the running list kept in an OPERATIONS panel that opens the round reading no operations. Undo, Reset and Submit sit under it, and the header keeps your place in the run of seven.

1. Press Start when you are ready. The two minutes belongs to the calculation and only begins here.
2. Read the target and the six numbers you were dealt.
3. Build one operation: two of your numbers and one of the four operators.
4. Watch the OPERATIONS panel, which lists what you have built so far. Undo walks a step back, Reset throws the round's working away.
5. Submit when you have hit the target or gone as close as the clock allows.
6. Move on to the next of the seven calculations. The header shows which one you are on.

The numbers round is one of the few arithmetic formats that stays tense for people who are good at it, because the target moves out of reach of clean maths on purpose and the clock is short enough to punish tidiness. Septonum serves seven of them in a row, which is the real design decision here: one is a party trick, seven is a session, and the EXACT counter in the stats gives the perfectionists something to chase across days rather than within a round.

Distance, not a pass or a fail. The brief asks you to get as close as possible, and the stats panel keeps EXACT as its own counter alongside DAYS and STREAK, so landing dead on the number is tracked separately from merely finishing a round. During a round the two things that move are the countdown, which runs from 2:00 with a bar under it, and the OPERATIONS list filling in under the operators.

The daily seven

The header numbers the day's puzzle and your place in the run, reading 1 of 7 on arrival, and the browser holds seven empty round slots stamped with the date.

With friends

The site's own description says you can play solo or with friends, and a two person button sits in the header beside a dumbbell.

• Do not press Start until you are actually looking at the screen. The clock is per calculation and it is stamped the moment you begin.
• A round is never lost, only scored, since the brief asks for the nearest you can get. When the clock is nearly gone, submit the closest thing you have built instead of reaching for the exact hit.
• Undo steps back one operation while Reset wipes the round's working, so count how far back the mistake is before you reach for the bigger button.