Rotato

Rotato is a number grid with one move in it. The line under the title says it plainly: spin the tiles to order the number grid. The move is a quarter turn of a 2x2 block, which cycles four tiles at once, each one corner around the block, and the target state is the numbers reading in order left to right and top to bottom. Under the title sit four chips, Easy, Medium, Hard and Devilish, and the day's date. The site's own notes place a 4x4 board at Medium and talk about work on 5x5 and 6x6 grids, and they measure a solve against a benchmark called Par.

1. Pick a difficulty from the four chips under the title: Easy, Medium, Hard or Devilish.
2. Start the day's board from the New Game control.
3. Turn a 2x2 block a quarter turn. That is the entire move set, and each turn moves four tiles one corner around the block.
4. Keep turning until the numbers read in order across the rows.
5. Watch Par, the benchmark the notes measure a finish against.

A puzzle with a single legal move is a rare thing, and it changes what solving means: you always know what you can do, and the whole difficulty lives in the order you do it. Every quarter turn cycles four tiles at once, so it never touches one piece in isolation, and the interesting play is learning to spend a move undoing your own damage on purpose. The Par line turns that from a finish into a score.

The page commits to the goal state, numbers in reading order, and a move count set against Par, and the site's own notes describe the grid going all green with the counter still green, which reads as tiles being graded in place rather than only at the end.

Easy

First of the four difficulty chips under the title.

Medium

The site's notes describe a Medium board as a 4x4.

Hard

Third chip. The notes discuss technique on 5x5 and 6x6 grids without tying either to a named chip.

Devilish

The fourth and last of the difficulty chips named on the chooser.

• Finish the top row first and then defend it. The game's notes are explicit that scattered repairs undo each other, because every turn you make somewhere else can reach back into a row you already ordered.
• Count the turn both ways round. A tile one corner from home lands in a single clockwise turn or a single counterclockwise one depending on which way is shorter, and both cost the same one move.
• Set up before you spin. An interior tile sits in as many as four overlapping blocks, so when a useful turn would break something already placed, move the placed tile out of the way first, turn, then put it back.