Shikaku
Puzzle · 8 playsShikaku
Cut the grid into rectangles — one number in each, matching its area.
About Shikaku
A partition puzzle from Nikoli built on one beautifully clean idea: divide the whole grid into rectangles so each contains exactly one number, and that number equals the rectangle's area. A 6 could be 1×6, 2×3, 3×2 or 6×1, and choosing correctly is the entire puzzle. Because every cell must belong to exactly one rectangle, the pieces constrain each other tightly — a careful opening usually makes the rest of the board fall out by itself. Free to play in your browser — no download, no sign-up.
How to Play
Drag across cells to draw a rectangle. Each rectangle must contain exactly one number, and its area must equal that number. Every cell belongs to exactly one rectangle — no gaps and no overlaps allowed.
Tips & Strategy
Begin with the numbers that have only one possible shape and position. A 1 is always its own cell, so mark them immediately. A prime number like 5 or 7 must be a straight line of that length, which usually only fits one way near an edge — and every prime narrows the board fast.
Use the other numbers as walls. No rectangle may contain a second number, so when you consider a placement for a 6, any orientation that swallows a neighbouring clue is dead. Scanning each number's legal orientations and keeping only those that avoid every other clue eliminates most possibilities before you draw anything.
Look for cells that only one clue can reach. Pick an empty cell, especially in a corner or a tight pocket, and ask which numbers could possibly extend to cover it. If the answer is exactly one, that clue's rectangle must include that cell, which often fixes its orientation outright. This 'who can reach this square' question is the single most productive habit in Shikaku.
Count areas when the board gets crowded. The clue numbers always sum to the total number of cells, so if a region is walled off with, say, eleven cells left and only a 4 and a 7 available, both must lie entirely inside it. And never commit an ambiguous rectangle early — draw the forced ones first and let the awkward clues inherit whatever space is left, because in a well-formed puzzle there is exactly one way for that to work out.