A two-and-a-half-minute mental-arithmetic round. Each card gives you a price, a basket and a promotion written the way shops write it, and you type what it is worth — as a percentage off, as the total you pay, or as the price of one item. Get it wrong and the full working opens up: list price, amount paid, and the conversion between them.
Discount Detective deals eight promotion cards a round. The first five are one-step offers — a spend-and-save threshold, second item half price, a bonus pack — and the last three take two steps: a threshold that fires again on every complete multiple, buy N get M free, and one discount applied on top of another. Every number on a card is generated for that card and stated on it, so nothing depends on local prices or sale rules. A round takes about two and a half minutes.
Type with the keypad on the stage: digits, a decimal point, delete, and submit. A physical keyboard works too — the number keys, the full stop, Backspace, and Enter to submit. You never type the unit: the input row carries a standing label and the question above it says the same thing in words. Submit stays disabled until what you have typed reads as a number, and a disabled submit is not a wrong answer — only the 20-second clock scores a card against you.
A correct card scores 100 points before multipliers, and the three harder cards are worth 1.4 times that. A streak raises the multiplier by half a step every two correct cards up to 2.5, which a flawless round reaches on the seventh card: eight out of eight is 1,680 points. A wrong answer or a timeout breaks the streak and takes nothing away — there are no lives and no way to be knocked out. There is no speed bonus, because the point of this game is arithmetic you can check, not arithmetic you can rush.
The round ends after the eighth card. The result page lists all eight — the promotion type, what you answered, and what it was really worth, with the misses marked — and collects the knowledge points behind the cards you missed. Your grade comes from how many you got right. Nothing is uploaded; your best score stays in this browser.
With no deal link in the address bar every round is dealt fresh. The share text carries a deal link, and opening it deals exactly the same eight cards with the same prices, the same baskets and the same questions — including in the other language, because the cards are generated from the seed rather than drawn from a list. Leaving the page mid-round saves where you were, including how much of the 20 seconds was left; coming back puts you on the same card.
English and Chinese ask the same question in different units, because the two languages state a discount differently: English asks for a percentage off, Chinese asks for 折 — tenths of the list price — to one decimal. The tolerance is set so both come to one percentage point, which is what makes the same seed the same difficulty either way. Prices, baskets and promotions are identical in both; only the unit of the answer changes.
However an offer is worded, it comes down to the amount paid over the ticket price; the percent off is one minus that ratio. Work out the amount paid first and the comparison becomes arithmetic instead of judgement.
50 off 300 on a 344 basket is not a sixth off. The 50 comes off 344, which is 14.5% — the threshold decides whether the discount fires, not how big it is.
'20 off every 100' on a 260 basket fires twice, for 40. The same wording without 'every' fires once. It is the single most expensive word on a promotion card.
Two at 45 with the second halved is 67.50 against 90 — 25% off, not 50%. On three items the same offer is worth about 17%.
Buy two get one free is three items for the price of two: 33% off, not 50%. Divide by what you take away, not by what you paid for.
20% off and then another 10% off is 0.8 × 0.9 = 0.72, so 28% off rather than 30%. The second discount only applies to what the first one left.
25% more for the same price means you pay for 125 units at the price of 100 — the unit price falls by 20%, not by 25%. Compare price per unit and the question disappears.
No. The input row carries a standing label and the question says the same thing in words, so you only ever type a number. If a unit slips in from a paste, it is stripped before the answer is judged.
One percentage point either side in English, and one tenth of a 折 in Chinese — the same width, stated in each language's unit. Where a card asks for money the band is a cent, or half a percent of the per-item price. The band is always wider than the rounding in the answer shown, and narrower than the common mistake, which is checked for every card before it ships.
That is a different question, and it is one with a local answer: what counts as a legitimate reference price is set by national rules, and they differ on how long an item must have been sold at that price. This game takes the list price as given and asks only what the promotion does to it.
Money Personality is multiple choice and diagnoses which kind of spending decision a round went wrong on. This one has no options: you do the arithmetic and type the number, and every card shows you the working afterwards. Different question, different skill.
Because a basket under the threshold is a real outcome, and the offer is still printed on the card. An offer below its threshold is worth exactly nothing, which is worth meeting once. At most one card a round is like this.
No. The round is generated in your browser from a seed, your best score is kept in this browser, and the share text carries only the grade, the score, how many you got right, your longest streak and the seed — never a card or an answer.
