Yes — Shikaku runs directly in any modern web browser, so you can play it without downloading, installing, signing up, or creating an account. The full Shikaku puzzle loads as a single in-page React game: a fixed 4 by 4 grid with five numbered clues, mouse or touch input for drawing rectangles, complete keyboard control for hands-off play, an Undo button, a Restart button, and a Boss Key. Nothing is fetched from a server after the page loads, no daily puzzle download is required, no random generator is invoked, and the game adds no extra package dependency to your browser. The board, the scoring, the two-error rule, and the unique partition are all stored inside the page itself, which means the same sequence of placements always produces the same 1,000-point finish on any device. That last point is what separates a true no-download experience from a wrapper that streams puzzles from a backend: every check that decides whether a rectangle is accepted runs locally in your browser, and the same checks are easy to reproduce from a saved copy of the page.
What "Playing Shikaku Without Downloading" Actually Means
The phrase covers several specific promises that browser puzzles do not always keep. A real no-download Shikaku experience has to avoid installers, app-store wrappers, ZIP archives, and large one-time downloads that mimic "free" games. It should also avoid account creation, email verification, captchas that require a sign-up, and any screen that demands a login before the first move. The Shikaku puzzle on this site meets each of those tests: the page opens, the 4 by 4 grid appears within the canvas, the score and mistake counter read zero, and the cursor is ready to anchor a corner cell.
Because the game runs as a small client-side React application, every check happens locally in your browser. The validation logic, the candidate generator that enumerates every legal rectangle for each clue, the exact-cover backtracker that proves the unique solution, and the deterministic scoring that awards 200 points per accepted region all execute inside the page. Your browser does not phone home, your grid state is not uploaded, and no telemetry identifier is attached to a placement. The trade-off for going fully local is that there is exactly one fixed 4 by 4 board — not a rolling daily download — which is also why the released fixture can be verified mechanically rather than spot-checked.
The 4 by 4 Board and Its Five Clues
The Shikaku release uses one compact 4 by 4 board authored specifically for this version. It contains five numbered clues whose values are 4, 4, 3, 2, and 3. Those five numbers sum to 16, which is also the total number of cells on the grid, and that equality is the structural backbone of the puzzle: every cell must end up inside exactly one rectangle, and the area of each rectangle is fixed by the number inside it. A clue of 4 could be a one-by-four horizontal strip, a four-by-one vertical strip, or a two-by-two block, while a clue of 3 can be a one-by-three or three-by-one rectangle, and a clue of 2 is necessarily a one-by-two or two-by-one domino.
The table below summarizes how many candidate rectangles each clue produces on this board before the overlap rule is applied.
| Clue value | Possible shapes on a 4 by 4 grid | Candidate count after filtering |
|---|---|---|
| 4 | 1×4, 4×1, or 2×2 | 2 |
| 4 | 1×4, 4×1, or 2×2 | 1 |
| 3 | 1×3 or 3×1 | 3 |
| 2 | 1×2 or 2×1 | 2 |
| 3 | 1×3 or 3×1 | 1 |
The filtered candidates, sorted by ascending size, are the input to the exact-cover backtracker. The backtracker tries one rectangle from the smallest candidate set, rejects every rectangle that overlaps the accepted cells, and continues until either all 16 cells are covered (a valid cover) or every branch dead-ends. Because the released board yields exactly one cover on a search that allows up to two, the partition is provably unique under the stated rules.
Touch and Mouse Controls
On a phone, tablet, or trackpad, placing a rectangle is a two-step gesture. You tap or click one corner cell, then tap or click the opposite corner of the rectangle you want to draw. The board highlights every cell between those two corners as a live preview. If the preview covers the span you intended, tap Place rectangle to validate the placement. If the preview is wrong, tap a different start corner to reset the selection or tap a cancel control to clear it. Large selection buttons sit alongside the grid so you do not need precise drag motion, and the four equal columns fit comfortably on a narrow screen.
On a desktop with a mouse, the same two-click flow applies: click one corner, move the cursor across the span, click the opposite corner, and click Place rectangle. The highlight updates as the cursor moves, so you can verify the span visually before committing. There is no need to drag — the game treats clicks as discrete anchors rather than as a continuous stroke.
| Action | Mouse or touch path | What happens on screen |
|---|---|---|
| Anchor first corner | Tap or click a cell | First corner is marked, no rectangle yet |
| Anchor second corner | Tap or click the opposite cell | Preview highlights the span |
| Validate | Tap or click Place rectangle | Rectangle is accepted if valid, mistake counter ticks up if not |
| Restart the selection | Tap or click another start cell | First corner moves to the new cell |
| Cancel the selection | Tap or click a cancel control | Preview clears, no corner anchored |
Playing Shikaku With Only a Keyboard
You do not need a mouse or a touchscreen to play. The Shikaku board is fully keyboard-accessible, which is the cleanest way to confirm the no-download promise — a keyboard-only session removes every input device except the one built into the laptop. Move the cursor with the Arrow keys until the focus indicator rests on the corner cell you want, press Enter to anchor that corner, move to the opposite corner with the Arrow keys, and press Enter again to place the rectangle immediately. There is no separate Place rectangle step in keyboard mode.
Three keyboard shortcuts cover the most common corrections. Press Escape to cancel a partial selection if your first corner was the wrong cell. Press U to undo the most recent accepted rectangle; the rectangle disappears and its cells become available again, but the mistake counter does not decrease. Press Escape twice in quick succession to open the boss screen, which is the same privacy gesture used by the other browser games on the site. None of these shortcuts require a focus shift, and none of them pause or freeze the score.
How to Solve the 4 by 4 Partition
The solution is a deliberate process, not a speed test, and the fixed board becomes easier with repetition because the clues do not change. Follow these steps to reach the 1,000-point finish on the released fixture:
- Open Shikaku in your browser and confirm the score reads 0 and the mistake counter reads 0.
- Scan the five clues and identify the one with the fewest candidate rectangles on the 4 by 4 grid. The disclosure lists 2, 1, 3, 2, and 1 candidates per clue, so start with a clue whose filtered count is 1.
- Anchor that clue's only legal rectangle. With touch or mouse, tap one corner cell and then the opposite corner, then choose Place rectangle. With keyboard, move to the first corner, press Enter, move to the opposite corner, press Enter again.
- Inspect how that rectangle reshapes the remaining space. Cells inside the accepted rectangle are now locked, and several candidate rectangles for neighboring clues may have been removed by overlap.
- Recompute candidate counts for the remaining clues given the locked cells, pick the next smallest candidate set, and place that rectangle next. Repeat until all five clues have one accepted rectangle each.
- Confirm that every one of the 16 cells is inside exactly one rectangle, that each rectangle contains exactly one clue, and that width times height equals that clue's value. The score should now read exactly 1,000.
- If a placement proves invalid, press U to undo the most recent accepted rectangle and try the next candidate for that clue. The mistake counter ticks up only on rejected submissions, not on Undo.
The disclosed golden partition that satisfies these checks uses rectangles spanning rows 1 to 2 with columns 1 to 2; rows 1 to 2 with columns 3 to 4; row 3 with columns 1 to 3; rows 3 to 4 with column 4; and row 4 with columns 1 to 3. You do not need to memorize that layout; the steps above reach it through candidate-count logic rather than recall.
Scoring, Mistakes, and the 1,000-Point Finish
The score is deterministic. Each accepted rectangle awards exactly 200 points, and a complete partition uses exactly five accepted rectangles, so 200 × 5 = 1,000, which is the maximum possible score. There is no bonus for finishing quickly, no penalty for using Undo, and no time multiplier. Because the score is computed locally from the accepted rectangles, the same sequence of placements always produces the same final value, which is what makes the score auditable from outside the game.
The mistake counter behaves just as strictly. An invalid submission is not placed and counts as one mistake; you can inspect the highlighted preview, read the rejection, and continue. A second invalid submission deadlocks the run until you press Restart, which returns the board to the original clues, clears the score, clears the mistake counter, removes every accepted rectangle, and removes the current selection. Both the 1,000-point completion state and the two-mistake deadlock state are terminal: later cursor movement, Enter presses, Place rectangle clicks, and Undo presses cannot change the frozen result, which prevents a lucky guess from saving a deadlock or a panic undo from erasing a finished puzzle.
Why the Released Board Stays a Browser Game
The combination of "no download" and "unique solution" only holds if the board itself is fixed. A daily download would require server-side state, which would either cost bandwidth, require an account, or both, and it would also make it harder to prove that the puzzle has exactly one partition because the test target would move every day. The choice to ship one Lizely-authored 4 by 4 fixture — not an official Nikoli puzzle, not a historic published board — is what makes the unique-solution claim honest. Nikoli is cited only for the rule set on the Shikaku rules page, and Simon Tatham's Rectangles documentation provides an independent description of the same core constraints, so the rules are not invented and the fixture is the only variable.
If you want to confirm that the no-download experience really works for a different browser-only puzzle too, the Can You Play Cryptogram Without Downloading? Yes guide walks through a sibling example in the same category. Beyond that, the Shikaku page itself is the only artifact you need — open it, draw the rectangles, watch the score climb to 1,000, and close the tab when you are done.
Related reading: Can You Play Skyscrapers Puzzle Without Downloading? Yes.