Shikaku: rules and how to play

Goal of the game

Divide the whole grid into rectangles. Each printed number tells you the area of the one rectangle containing it.

Rules

• Every cell belongs to exactly one rectangle: no gaps and no overlaps.
• Rectangle sides follow the grid lines. A square is also a rectangle; an L-shape is not.
• Each rectangle contains exactly one clue, and its area, width × height, equals that clue. Count the clue cell as part of the area.
• The clue can lie anywhere inside its rectangle, not necessarily in a corner. A clue 1 occupies just its own cell.

A small example, step by step

1. For a clue 6, list the possible dimensions: 1×6, 6×1, 2×3 and 3×2.
2. Suppose the still-uncovered space around this clue is a 2-row by 3-column corner pocket, bounded by the board edges and already confirmed rectangles.
3. If that pocket contains no other clue, its six cells must form the 2×3 rectangle of the 6.
4. This is a local example: a 6 without those boundaries does not automatically force 2×3.

Beginner deductions

• Start with 1s and clues with only one legal rectangle placement.
• For each clue, reject placements that leave the board, contain another clue or overlap a confirmed rectangle. Check positions as well as dimensions.
• If an uncovered cell can belong to only one remaining clue placement, that rectangle is forced. Shared cells of several candidates can restrict neighbours without proving which full rectangle is correct.

Common mistakes

• Do not read a clue as perimeter or side length.
• Do not accept a six-cell L-shape for 6, or a rectangle with two clues.
• Do not assume every rectangle starts at its clue. Cover the whole board, including cells far from numbers.

Controls and availability

The current DEV preview has a player for this game. Availability depends on published review grids; this is not a general release or approval of all four levels.

Drag between opposite corners, or tap one corner then the opposite corner. A single tap on a clue 1 places its rectangle. Escape cancels a pending selection. A new rectangle replaces overlapping rectangles. Undo reverses the last edit; Clear all asks for confirmation. Pause/Resume and Check remain available. Hints and revealing the solution require confirmation and count as assistance.

Difficulty

The intended difficulty contract is Easy, Medium and Hard solved entirely by logical deductions, with zero hypotheses. Hard may require longer chains or more demanding techniques. Expert may allow an explicit hypothesis, following its consequences and rejecting it if it contradicts a rule. A unique solution alone does not prove a logical solving path. Unclassified means not yet graded, not automatically Expert. Human calibration remains pending; these are requirements, not a claim that all bands are available.

FAQ

Do I need Premium to read this guide?

No. Reading the rules is public; playing the new game requires Premium.

Does a difficulty label guarantee a calibrated game?

Not during this preview. Human review is pending. The intended distinction is deductions only for Easy/Medium/Hard; hypotheses may be used in Expert.

What if I cannot find a move?

Recheck the rules and the last certain steps, then revisit the deductions above. Keep possibilities separate from confirmed answers; being stuck is not proof that guessing is necessary.