Shikaku

The basics

Press on a cell and drag to the opposite corner of the shape you want, then release. The shape must stay inside the grid, may not cover a cell that is already used, must hold exactly one number, and its area (height × width in cells) must equal that number — the live label shows the area while you drag. A one-cell shape is only legal on a 1. Tap a rectangle once to remove it. Undo steps back one shape, Hint paints one rectangle from the stored solution and counts itself, Restart clears the board, and the arrows in the top bar move between boards. The Easy / Medium / Hard chip switches size. A number of 12 allows shapes such as 3×4, 4×3, 2×6 or 1×12, so thin strips are worth trying. When no solution shape can still be placed the status line says the board is a dead end; undo and try another split. Solved boards and your best times stay in this browser only. Add ?puzzle=7 or ?level=hard to the address to pin a board.

Objective:

Partition the whole grid into rectangles. Every rectangle must contain exactly one number, and its area in cells must equal that number; every cell must end up inside exactly one rectangle. The board is won when all cells are covered and every shape is legal. There are 36 boards: 5×5 on easy, 7×7 on medium and 9×9 on hard, twelve of each. Each board was checked before shipping to have exactly one solution, so a legal shape that leaves the rest of the grid impossible is a dead end rather than an alternative answer.

Controls:

Drag with a mouse, a finger or a pen between two cells; the same gesture draws the rectangle. A tap on a rectangle removes it. Buttons: previous / next board, the size chip (Easy / Medium / Hard), Undo, Hint, Restart and Rules. Keyboard: U undo, H hint, R restart, N next board, Left / Right arrows change board, Esc closes the rules. Every button is at least 26 px tall, the grid uses touch-action none so a drag never scrolls the page, and the board rescales to the stage on the 348×261 phone frame, the 390×844 portrait frame and the 894×670 desktop frame.