Dormice.

Every dormouse in the copse keeps one store in one tree, and in the bigger puzzles wakes in one week of the spring. There are as many stores, trees and weeks as there are dormice, and no two dormice share any of them.

Every numbered clue beside the grid is true, and the clues together leave exactly one way to match everything up.

The grid is your notepad. Each small square joins one item on the left with one item above: put a cross in it when you know the two do not belong together, and a tick when you know they do.

As soon as a tick goes into a square, every other square in that row and in that column of the same small table is a cross, because each item belongs to one dormouse and to no other.

Ticks carry from table to table. If Pip keeps the sloes and the sloes are in the elm, then Pip woke in the elm, and anything the sloes are not, Pip is not either.

The weeks run in order, one week apart, so a clue that says two weeks earlier means exactly two steps along the week column, and a clue that says earlier without a number means any number of steps.

One store went missing from the shared larder overnight. Nothing has to be guessed: every square can be reached from the clues by reasoning, and when the table is full the last line tells you who had it, where and when.

Tap or click a square: once puts a cross, twice a tick, three times clears it. The cross comes first because there are three of them for every tick. A tick fills the rest of its row and column with crosses by itself, as one step you can take back with a single Undo; you can switch that off in Settings.

Tap a header, or a name in the list under the grid, to outline that item everywhere it appears. Tap a clue to strike it out once you have used it; that is your own note and Undo takes it back too.

Check first tells you how many of your ticks are wrong and which table they are in. Press it again and it marks them. Crosses are never counted: one wrong tick poisons dozens of squares and the number would say nothing useful. Hint names the technique and the place, then fills in exactly one square. Hints and checks are free, counted and shown when you finish. Clear empties the grid; the clock keeps running.

Keyboard: arrows move with a wrap at the edge, Space or Enter cycles the square, X crosses, D ticks, Delete or Backspace clears, [ and ] jump to the previous or next table, Escape drops the selection, P pauses. U and Ctrl+Z undo, R and Ctrl+Shift+Z redo.

The clock runs from your first move to the last square and pauses when you leave the tab, which also hides the grid but never the clues: the clues are the rules of the day, not the answer. 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.

Monday and Tuesday are easy: three categories of five, no weeks. Wednesday and Thursday are medium, Friday and Saturday hard, Sunday the challenge, all of them four categories of four. Hard and Sunday are not bigger than Wednesday, they are harder: the clues get weaker, the order clues get vaguer, and on Sunday one square is only settled by testing an assumption until it breaks.

The size stops at twelve columns on purpose. At 390 px of screen a square is then about 29 px across, above the 24 px a finger needs, so the whole staircase fits on a phone and a fact carried from one table to another is a move of the eye. The book prints the same sizes as the game.

The week strip under the grid takes you to the other days; the archive goes back a year, and the practice sets have eight copses of each level with no date attached.

Start with the clues that name two items outright: a tick or a cross goes straight in, and the tick brings a row and a column of crosses with it.

When a row of a small table has one square left without a cross, that square is a tick. The same goes for a column: if only one dormouse can still take an item, it is that dormouse.

The move that makes this puzzle what it is: a tick joins two rows across the whole staircase. If Pip keeps the sloes, then everything the sloes cannot be, Pip cannot be either, in every other table.

Order clues fence the weeks in from both ends. Two weeks before someone means the first item cannot be in the last two weeks and the second cannot be in the first two.