A closer look at Rectangle Rooms
Area, not perimeter
A clue gives the number of cells in its room. A six may occupy two columns and three rows, for example. Count width times height; do not count the boundary length. Each room must be a rectangle aligned with the grid, including a one-row or one-column rectangle. Squares are rectangles too. Every cell must belong to exactly one room and every room must contain exactly one printed number.
Choose two opposite corners
Click or tap the first corner cell, then the cell at the opposite corner. Either diagonal order is accepted. The first corner has an outline and a pressed-state label. The second choice commits a valid rectangle or explains why it was refused, then clears that first selection. To cancel before choosing a second corner, use Cancel first corner; cancelling adds no edit. Selecting the same cell twice proposes a one-cell room, which is valid only for a clue of one.
Local checks are not a solving hint
A proposed room is refused if it has no clue, more than one clue, the wrong area, or overlaps an existing room. Refusals add no edit. A locally valid room can still prevent the rest of the puzzle from being solved. The interface checks the shape you entered; it does not choose the correct room or search for a compatible full solution before accepting your move.
Remove, undo, or retry deliberately
Remove a room switches to removal mode: select any cell inside that room to delete the entire rectangle. Removing a real room counts as one edit; choosing an unassigned cell removes nothing. Select Remove a room again to return to drawing. Undo last edit reverses one accepted placement or removal, reduces Edits by one, and clears a first-corner selection. Retry this board removes all rooms, history and selection, returns to drawing, and keeps the same clues.
Read without relying on colour
Tab reaches the cell buttons; Enter or Space selects a corner. Arrow keys move to the neighbouring cell without drawing, stopping at the boundary. Each cell label states its row, column, clue and room membership. The Room ledger lists both corners, dimensions and area for every accepted room. Visible thick borders separate rooms; colour is an additional cue rather than the only explanation.
Finish the whole partition
Completion requires every one of the sixteen cells to belong to a valid room, without overlap. There is no target score, timer or required order of rooms. After the final placement the cells lock and focus moves to Undo. Undo reopens the previous partial partition; Retry starts the same puzzle again. Edits counts changes to rooms, not individual corner selections or mouse clicks.
A finite, checked collection
New puzzle moves to another of seven prepared four-by-four clue sets and resets your attempt; the collection eventually repeats. Each has been checked for one complete valid partition. This is not an unlimited generator or a measured difficulty scale. Load beginner board restores the exact first lesson example. The beginner guide has a complete four-room answer and step-by-step controls to reproduce it.
Our implementation and your attempt
Rectangle Rooms follows the common numbered-rectangle area-partition mechanic described by Nikoli as Shikaku. Our program, clue placements, diagrams and explanations are made for this site; no affiliation or invention of the common rules is claimed. Rooms and selections stay in memory in this tab. Refresh loses your attempt; a fixed practice address reloads its board with no rooms. No account, payment, saved score, advertisement action or server submission of room choices is required. No health or general ability benefit is promised.
Common questions
Can one room contain two numbers if their sum matches its area?
No. A room contains exactly one number, and that one number must equal its area. Adding the values of several clues does not make a valid room.
Are one-cell and single-row rooms allowed?
Yes, when their area equals the sole clue they contain. Select the same cell twice for a one-cell room; use the two endpoints for a row or column.
Why was a valid room later in the wrong place?
Local validity does not guarantee that all remaining cells can be partitioned. Undo or remove it, then test a different rectangle.
How do I return to the tutorial example?
Choose Load beginner board or use its practice entry beside the lesson. Retry keeps the current clues; New puzzle changes them. A refresh clears rooms and history.