Hares.

Fill the meadow so that every row, column and block has each number once. Hares leap like a chess knight: two burrows a knight's leap apart never hold the same number. From Friday on, hares also refuse to sit next to the same number in any direction, corners included.

A knight's leap is two burrows one way and one across, the move a knight makes on a chessboard. It reaches over rows, columns and blocks alike, which is where the puzzle differs from the number square you already know: a burrow far away can still rule a number out.

The numbers the meadow gives you are heavier and sit a shade darker. Every meadow has exactly one filling that fits every rule. When the last burrow is right, the game notices by itself.

Tap or click a burrow to pick it, then a number from the pad under the meadow. Tapping the same number again takes it back, so the way out is always one tap away. Hold and drag from a burrow that already holds a number to write that same number into the empty burrows you pass. Nothing lights up while you play: finding a mistake is part of the puzzle.

Notes switches the pad to the small numbers you keep while you think; a number written for real clears the notes it rules out. Holding a pad number for half a second writes it the other way round, so you can drop a real number in without leaving notes, or pencil one in without entering them. Check first tells you only how many numbers are wrong and which rows or columns they sit in; press it again and it marks them. Hint names the rule and the place without giving the number away, and the second press writes that one number and explains it. If something on the board is already wrong, the hint points there first. Hints and checks are free and counted, and shown when you finish. Clear empties the meadow back to the numbers it started with; the clock keeps running and one Undo brings everything back.

Keyboard: arrows move from burrow to burrow, the number keys write a number, Shift plus a number writes it the other way round, a note while notes are off and a real number while they are on, N or Enter switches notes on and off, Delete or Backspace empties the burrow, Escape lets it go, U or Ctrl+Z undo, R or Ctrl+R redo, P pauses.

Pick a burrow and the meadow shades what a hare can reach from it, the knight's leaps and, on the king days, the burrows touching it. That shading is a help while you look, never a judgement, and Settings turns it off. The clock runs from your first number to the last burrow and pauses when you leave the tab or sit still for a minute, which also hides the meadow. Your progress, time, history and day streak stay in this browser, and in your account when you are signed in, so you can continue on another device. The day turns over at midnight where you are. Only the meadow of the day counts towards the streak, the archive is for practice; once you are five days in, a single missed day is forgiven, at most twice a month.

Monday and Tuesday are easy: six by six, blocks of two rows by three columns, numbers 1 to 6, with the knight's leap. Wednesday and Thursday are medium and Friday and Saturday hard, both nine by nine with blocks of three by three; from Friday the touching rule joins in and fewer numbers are given away. Sunday is the challenge, the same nine by nine with both extra rules and the fewest numbers to start from. The week strip under the meadow takes you to the other days; the archive goes back a year, and the practice sets have eight meadows of each level with no date attached.

Difficulty is measured, not guessed. Every meadow is solved by a program that only knows named rules, in three layers: the plain ones (a burrow with a single number left once its row, its column, its block and every hare within reach have taken theirs, and a number that fits only one burrow of a row, a column or a block), the patterns (a number held in place by the knight's leap or the touching rule alone, a pair of burrows holding two numbers between them, a number confined to one line inside a block), and the hard one (writing a number in, following it one step and dropping it because it runs into a contradiction). Easy and Medium never need that third layer; Sunday leans on it the most.

Start where the meadow is crowded. A block with six or seven numbers in it usually gives the rest away, and every number you write there narrows two more lines at once.

Then use the leap. When a row is missing a number and two of its empty burrows sit a knight's leap from that same number elsewhere, the third burrow is the only one left. That step is the heart of this puzzle, and the classic number square has nothing like it.

On the king days, look at pairs of touching burrows first. Two burrows side by side or corner to corner cannot both hold the same number, which quietly halves a lot of choices around a block edge.

When a number can only sit in one row of a block, it is gone from the rest of that row everywhere else on the board. That is often the step that unlocks a stubborn corner.