How to play SpotOn, the daily numbers game

If you have ever watched a contestant juggle a handful of numbers to hit a three-digit total, you know the spirit of SpotOn: a few small numbers, maybe a big one, four operations, and a target that looks unreachable until suddenly it isn't.

SpotOn makes it daily: five puzzles, laddered from a gentle warm-up to a genuinely tough finale. Everyone plays the same draws on the same day, and every target is checked by a solver before it goes out: there is always at least one exact answer to find.

A new grid arrives at 01:00 Paris time, every day of the year. That is midnight UTC in winter and 23:00 UTC in summer. If you started the previous day's grid late, it stays playable for two more hours after the switch before the game sends you to the new one.

• Five targets, played in order. You only see the next one once you have submitted the current one.
• Each target comes with its own six numbers. There is no shared pool across the day: every target is a fresh draw.
• The numbers come from a set of 24 tiles: 1 to 10 twice each, plus 25, 50, 75 and 100 once each.
• Difficulty climbs: the first target sits between 20 and 100 and falls in two steps, while the last can go up to 999, can't be cracked in fewer than four steps and has very few ways in.

Besides the five targets, the same site has daily logic puzzles, each with its own grid of the day: Sudoku, Nonogram, Math cages, Futoshiki and Binary.

An operation takes three taps: a tile, an operator, another tile. The two tiles merge into one new tile holding the result, which you can then use in later steps. On a keyboard, keys 1 to 6 pick tiles and + − * / pick operators.

• Each tile is used at most once. Once two tiles are combined, both are gone and only the result remains.
• You don't have to use all six numbers. Many targets fall with three or four of them.
• Every result must be a positive whole number. A subtraction that gives zero is refused, and so is a division that leaves a remainder: 9 ÷ 2 won't go, 100 ÷ 4 will.
• Order doesn't matter for − and ÷: the game always takes the larger number minus, or divided by, the smaller one. You can never produce a negative number by accident.
• Results can grow past 999 if you need a big intermediate value.
• Five operations at most: enough to merge all six tiles into one.
• Undo removes your last step, Restart clears the board. Both are free.

The moment any tile on the board equals the target, the game submits it for you. If you can't get there, the « Submit closest » button submits your closest tile instead. It asks for confirmation: the first tap arms it, the second submits.

Spot on earns a full star, close earns half a star, anything further earns nothing (the game still tells you how far off you were).

Close means within 2 % of the target, rounded up, and never less than 1. The screen spells out the window for each target in plain numbers. For a target of 120 you need to be within 3; for 683 the window is 14; for anything under 50 it is just 1.

Stuck? The hint reveals the first operation of one shortest solution. Taking it is optional and has a price: a target hit after the hint is worth half a star, even if you land exactly on it.

When a target ends close or missed, the game shows you one exact solution, so you learn something even from a miss; at the end of the day, the receipt lets you open the solution of every target. At the end of the day your results are tallied: five full stars is a perfect day, three or four is a good one. Your streak counts every day on which you submit all five targets, whatever your grades.

A timer runs on screen with two readings: the time spent on the current target and the running total for the day. The timing is kept by the server, from the moment a target opens to the moment you submit it, so closing the page doesn't pause it.

Time is purely for bragging rights: it appears on your end-of-day receipt and in what you share, but never changes a grade.

Here is an invented draw: target 683 with 75, 9, 6, 4, 3 and 1.

Start from the biggest lever. 75 × 9 = 675, which is only 8 short. Now build an 8 from what is left: 6 + 3 = 9, then 9 − 1 = 8. Finally 675 + 8 = 683. Spot on in four operations, with the 4 left unused.

There is a second road. Working backwards, 683 sits one below 684, and 684 is 76 × 9. So: 75 + 1 = 76, 76 × 9 = 684, then 4 − 3 = 1 and 684 − 1 = 683. Also four steps, and every intermediate result is a positive whole number.

And if you had stalled at 675? You would be 8 away, inside the window of 14, and still bank half a star.

• Find the nearest easy multiple first. Which product of your numbers lands just beside the target? Then the job shrinks to fixing a small gap.
• Work backwards. Write the target as a multiple plus or minus a little: 683 = 684 − 1 = 76 × 9 − 1. The leftover small number is often easy to build.
• Make the big number bigger. 100 + 1 or 75 + 1 before multiplying shifts a product by a whole multiple of the other factor, which is a quick way to aim.
• Save your small tiles for the finish. A 1, 2 or 3 left at the end lets you nudge a result up or down. Spending them early often leaves you stuck one away.
• Build the correction separately. Instead of chasing the target in one line, make the gap in a side calculation (6 + 3 − 1 = 8) and add or subtract it at the end.
• Bank the half star. When a target resists, check the close window on screen: if your best tile is inside it, submitting keeps half a star instead of risking nothing.