Pair Sums

Ten number cards lie face up in a single line, and above them a ladder of targets. Take two cards that are next to each other and add up to the target showing now; they leave, the row closes up, and the target climbs by one. Five takes and the row is empty. The catch is in the closing: two cards that were never neighbours become neighbours the moment a pair between them is gone, and the target has moved on by then.

It runs entirely on your device: 0 network requests, works offline. No ads, no account, nothing to buy, and no betting, money or prizes of any kind.

1. Focus the board — click it, or press Tab until it is focused.
2. Read the ladder. The target with the caret is the one in play; the ones after it are what the later takes will need. Planning is mostly reading ahead on that ladder.
3. Move the selected pair with Left and Right. Two cards are always selected — the one with the ring and its right-hand neighbour — and both carry a small triangle so you can see the pair rather than infer it. Up and Down jump to the first and last pair in the row.
4. Take the pair with Enter. If the two numbers add to the target the cards leave, the row closes up, and the next target lights. On a phone, tap a card to select its pair and tap again to take it.
5. Watch the tries. A pair that does not add to the target costs one try, and the line under the board tells you what the two cards actually made. You get three to five tries depending on how many near-misses the row contains.
6. Mind the order. A pair that adds to 12 is useless while the target is 10, and if you spend one of its cards on something else it is gone. Every deal here has at least one opening take that looks fine and kills the row.
7. Win by emptying the row. If the tries run out, or no two neighbours add to the target any more, the round ends there and says which of the two it was.

How do you decide which pair to take first in an adding-pairs card puzzle?

Work forwards along the target ladder rather than grabbing whatever adds up now. The question is not "which pair can I take?" but "which pairs do the later targets need, and does this take destroy one of them?" Two habits do most of the work. First, before you take anything, look at what closing that gap would join together — the two cards on either side of the pair are about to become neighbours, and that new pair is often the one the next target wants. Second, treat a card whose partner appears only once in the row as spoken for: if the ladder ends on 14 and there is exactly one 13 and one Ace, those two are already committed and any take that separates them ends the round. Openings that add up but strand something are the whole difficulty of the game, and every deal is built to contain at least one.

Is every row actually clearable?

Yes, and by construction rather than by luck. Each row is built backwards from an empty line: the pair for the last take is inserted first, then the pair for the take before it, and so on, each one dropped in as a unit at a random spot. The last pair inserted is therefore still side by side when you start, and it adds to the first target — so taking it returns the row to exactly the state it had one insertion earlier, where the same thing is true again. Undoing the insertions in order is a complete legal winning line, and the tests replay it through the same rules the game uses.

Why does the target climb instead of staying the same?

Because with a fixed target the puzzle disappears. If every take needs the same total, then a row that can be cleared can be cleared in any order at all — swapping which card pairs with which always works out, so no take can ever be a mistake and the game becomes a spotting drill. Moving the target by one after each take breaks that, and it is what makes the order of your takes the actual puzzle. The build checks this: it generates rows against a fixed target and proves none of them can be stranded, which is the reason the shipped game does not use one.

Do the suits mean anything?

No. Spades, hearts, diamonds and clubs are decoration and nothing in the rules reads them — a 7 of clubs behaves exactly like a 7 of hearts. They are printed because a number with a suit reads as a card rather than as a digit in a box. If you catch yourself looking for a suit pattern there isn't one, and the screen reader deliberately never announces them.

What happens if nothing adds up any more?

The round ends immediately and is scored as a loss, with the reason said out loud. A row where no two neighbours reach the target cannot recover, and letting you discover that by trying every pair in turn would be worse than telling you. It is also the lesson: a dead row is never a bad deal, it is a take that spent a card the ladder still needed.

Is there any money, betting or in-app purchase in this?

None, and there never will be. The cards are numbers on tiles: no currency, nothing to buy, no wager of any kind, and no gambling mechanic anywhere in the game. There is no score to buy your way up and no advert to sit through.

Does it work offline, and can I play it by keyboard or screen reader?

Yes to all three. Once the page has loaded once the whole game is on your device — the generator, the rules, the copy — and nothing is fetched while you play. Arrows move the selected pair, Up and Down jump to the ends of the row, Enter takes. Every card announces its number and its position, the ladder announces which target is taken, live and still to come, and the board says how many cards and tries are left. Selected, taken and dead states each carry a glyph and a word, so nothing depends on telling one tint from another.

Ten cards, five takes, values from 1 to 13, and one rule: the two cards must be neighbours and must add to the target showing now. The ladder starts somewhere between 8 and 11 and climbs by one each take. The minimum number of takes is always exactly five — every take removes two cards, so there is no shorter route to find — which is why the budget in this game counts wrong attempts rather than moves. Equal cards do not pair unless they happen to add up, and there is no undo: a take is spent.

Deal Sum is the other arithmetic card game here — four cards from a grid that reach a target, with no adjacency to worry about. Card Ladder is the other single-row card puzzle, and it is about ordering rather than adding. Sum Links works the same complement arithmetic on a grid instead of a line.

Bookmark this page (Ctrl+D, or ⌘D on Mac) or install the app — it works offline the next time you need it.