Hedgehogs.

Place exactly two hedgehogs in every row, every column and every flowerbed (the outlined regions). A garden with nine rows has nine columns and nine flowerbeds, so eighteen hedgehogs in total; the size changes through the week, from eight by eight on Monday to ten by ten from Friday.

No two hedgehogs may touch: not side by side, not diagonally. They prickle.

A dot is your own note that a cell stays empty. When you place the last hedgehog, the game checks the solution by itself.

Tap or click a cell: once for a dot, twice for a hedgehog, three times to clear it. Hold the button or your finger and drag to sweep dots over many cells at once. A hedgehog that breaks a rule turns red.

Check first tells you only how many marks are wrong. Press it again and it shows which. Hint outlines the next step a patient friend would point at and explains it; press it again to fill it in. Hints are counted and shown when you finish. Reset empties the garden and the clock.

Keyboard: arrows move, Space or Enter cycles the cell, X dot, H hedgehog, Delete or Backspace clears, P pauses. Undo takes back the last move.

The clock runs from your first move to the last hedgehog and pauses when you leave the tab. Your progress, time, history and day streak stay in this browser.

Monday and Tuesday are easy (eight by eight), Wednesday and Thursday medium (nine by nine), Friday and Saturday hard (ten by ten) and Sunday is the challenge: the hardest of the candidate gardens for that date. The week strip under the garden takes you to the other days; the archive goes back a year, and the practice sets have eight gardens of each level with no date attached.

Difficulty is measured, not guessed: the program plays every candidate garden with the same hints you can ask for and counts how often it gets stuck. Easy days never get stuck, Sunday gets stuck most.

A flowerbed that fits inside one row or one column holds both hedgehogs of that row or column, so every other cell in that line is empty.

Two flowerbeds that together cover exactly two rows use up all four hedgehogs of those rows. Any cell of a third flowerbed inside those rows is empty.

A hedgehog empties all eight cells around it. When a flowerbed has only a few cells left, count how many hedgehogs still fit without touching.