Yukti, a daily logic puzzle at playyukti.com, gives everyone the same puzzle each day. Every move must be a certain deduction, so there is never a reason to guess. If a move breaks a rule, the board stops you and says which one. When you're stuck, a nudge asks you a question.
What kinds of puzzle are there?
Each kind shows up in two settings. The story changes; the rules stay the same. Spotting the kind is part of the fun.
How do crossings work?
A river crossing, or a lift between floors.
Goal: get everyone to the other side: the far bank, or the top floor.
How: tap a passenger to put them in the boat or the lift, then tap Row across or Go up. Keyboard: Tab to a passenger, Enter to load, R to go.
Blocked: anything that would leave a forbidden pair alone, overfill the boat or go over its weight limit. Yukti says which rule.
How do liars and truth-tellers work?
Knights and knaves on an island, or honest and faulty robots in a workshop.
Goal: work out who always tells the truth and who always lies.
How: choose Knight, Knave or Unknown for each one. A mark is accepted only when the statements make it certain.
Blocked: a mark that doesn't fit is stopped, and Yukti says which statement it breaks. It still counts as a step.
How do logic grids work?
A plain grid of people and their things, or the spirit's riddle: a tale that ends in a question. The riddle is after the Vetala Panchavimshati (tales of a king and a spirit, c. 11th century).
Goal: work out which item in each category belongs to each person.
How: pick a cell. Rule it out as a free note, or Confirm the pair when you're certain. Only confirming counts. Keyboard: arrow keys to move, [ and ] to switch categories, X to rule out, Enter to confirm.
Blocked: a confirm that doesn't fit is stopped, and Yukti says which clue it breaks. It still counts as a step.
How does sound or fallacy work?
Short arguments about places and signs, or about villagers and their habits.
Goal: mark each argument Holds, or say what breaks it. Take what you're told as true, even where it sounds odd.
How: tap one of the answers under an argument: three on Gentle days, five on Steady, all six on Tough. Keyboard: Tab to an argument, arrows between answers, Enter to mark.
Blocked: an answer that isn't certain is stopped, and Yukti says what doesn't hold, with the lines that show it. It still counts as a step.
What do the six answers mean?
- Holds
- The reason is true here, and the rules carry it to the claim.
- Reason not shown
- Nothing you were told shows the reason is true here.
- Has an exception
- Somewhere has the reason but not the claim.
- Proves the opposite
- The rules lead from the reason to the claim being false.
- Evenly matched
- Another reason true here points the other way just as well.
- Contradicted
- You were told the claim is false here.
These six are a simplified, checkable reading of the Nyaya Sutras (1.2.4): “Reason not shown” is sadhyasama, “Has an exception” savyabhicara, “Proves the opposite” viruddha, “Evenly matched” prakaranasama and “Contradicted” kalatita, in its later reading. An argument has five parts: the claim (pratijna), the reason (hetu), the example (udaharana), the reason applied here (upanaya) and the conclusion (nigamana).
How does the counting duel work?
A duel of numbers at King Janaka's court, against Bandi, or a game of stones on a riverbank, against the ferryman.
Goal: make the last move. In a reverse duel, leave it to the other side.
How: tap an amount to add it to a count, or to take that many stones. The other side replies at once. Keyboard: Tab to an amount, Enter to play it.
Blocked: a move that would let the other side make the last move is stopped. It still counts as a step.
At King Janaka's court, the boy Ashtavakra met the debater Bandi in a duel of numbers.
What is a nudge?
A question that points you at the rule you're missing. You get three per puzzle: the first asks, the second narrows it down, the third names a step. They never count against you.
What does the share grid mean?
One square per step, so friends see the shape of your solve, not the answer.
- Carried a passenger, or a certain mark
- Rowed back alone
- Blocked attempt
- Solved
Every attempt counts as a step, including ones you undo. Thinking first is free.
How does difficulty change through the week?
- GentleMonday and Tuesday
- SteadyWednesday and Thursday
- ToughFriday to Sunday
Weekend puzzles are bigger and take longer.
How do streaks work?
Solve on the day to keep your streak. One missed day in any 7 is a rest day and keeps it going.
Is it a test?
No. There are no grades. The shortest route is a target to aim for, not a score to pass.