Getting your game ready…
Divide the whole grid into rectangles. Each rectangle contains exactly one clue, and its area in cells must equal that number. A clue of six might belong to a one-by-six, two-by-three or three-by-two rectangle if the board has room.
Select two opposite corners to draw a rectangle. Use taps or clicks, or move with arrows and choose with Enter or Space. Escape cancels the first corner. Delete or Erase rectangle removes the selected region before you redraw it; Z undoes the last change.
Every cell must belong to one rectangle, with no overlaps and no extra clue inside a region. The two easier boards use five-by-five cells; the other four use six-by-six. A locally correct area can still leave an impossible gap elsewhere.
Factor a clue into pairs of side lengths, then rule out rectangles that leave the board or contain another clue. A narrow space beside the edge can make a large clue much more restrictive than it first appears.
Before committing a rectangle, inspect the cells just beyond it. Every remaining patch must still reach a clue and fit into a rectangle. A small isolated pocket is a useful warning that one boundary belongs elsewhere.
Shikaku asks you to place whole regions instead of individual answers. Six fixed layouts make the rectangle boundaries the main object of play. Exact grid lines and clue numbers remain visible while you compare shapes. After solving, Undo reopens your last change; Next puzzle waits for your choice. Completed puzzles and the selected board are remembered, but unfinished rectangles are not restored when you reopen.