Shikaku

Shikaku is a puzzle you solve by drawing boxes. The daily board is ten cells by ten, scattered with numbers, and the job is to cut the whole grid into rectangles so that each rectangle contains exactly one number and that number equals its area in cells. Every cell has to end up inside exactly one rectangle, which is what turns a drawing exercise into a proof. The page is built around the clock rather than around attempts: three counters sit above the grid for streak, best time and puzzles solved, a timer starts when you press START, a countdown under the board shows when the next puzzle lands, and the day's leaderboard runs down the right hand side ordered by finishing time. The line under the board spells out the controls, which are all pointer work: drag to draw, click to place a 1, right click or click an existing rectangle to erase.

1. Press START. The timer beside the board size starts with it.
2. Drag across the grid to draw a rectangle.
3. Click a single cell on its own to place a 1, which the control line offers as its own gesture.
4. Right click a rectangle, or click one that already exists, to erase it.
5. Keep cutting until every cell belongs to exactly one rectangle and every rectangle holds exactly one number equal to its area.
6. The leaderboard button reads SOLVE TO SUBMIT, so a time joins the standings once the grid is finished.

Most logic puzzles are solved by writing marks into cells. Shikaku is solved by cutting territory, and the difference is real: a clue is a shape looking for somewhere to sit, and the deduction happens between rectangles that cannot both fit rather than inside a single square. The site pushes that toward speed rather than contemplation, with a timer that starts on the button, a streak and best time above the grid, and a leaderboard for the day ranked by how fast the grid fell.

Measured against a clock rather than against attempts. The three counters above the board wait for a finish, so the only live signal during a solve is the timer. The judgement is social rather than corrective: the day's standings sit beside the board ordered by completion time, with a share control next to reset, and the entry button under the list reads SOLVE TO SUBMIT.

Daily

One board a day, ten by ten, described on the page as the same for everyone worldwide, with a countdown to the next one under the grid.

Play

A separate nav entry beside Daily. The site's own description promises unlimited practice.

Archive

A nav entry for past puzzles.

• Then take the primes. A prime clue can only be a one cell wide strip, across or down, so its shape is settled before you start and only its position is in question.
• Remember that every cell must end up covered. An empty square hemmed in by finished rectangles is not a leftover to deal with later, it is proof that one of the rectangles around it is wrong.