Both puzzles ask the solver to cut a grid into regions. That is where the resemblance ends. One prints numbers and asks for rectangles. The other prints dots and asks for shapes that spin around them. A shopper can tell them apart at thumbnail size, which is exactly why a listing that shows the wrong puzzle gets returned. If you sell both, treat them as two different products, not one listing with two skins. Which of the two to build is a separate question; this page is what each title must show once you have chosen.
Shikaku — a number is an area
Shikaku prints numbers in a grid. The solver divides the whole grid into rectangles. Every cell ends up inside exactly one. Each rectangle holds exactly one number, and that number is the rectangle’s area. So a 6 is a 1×6, a 2×3, a 3×2 or a 6×1 — and only one of those will let the rest of the grid finish.
The board size is the product. Rows and columns run 4 to 20 and open at 7×7. Lock to square is ticked by default, so a run comes out square unless you say otherwise. You will not find an easy/medium/hard dropdown — the group labelled Difficulty holds the grid controls, the Larger areas dial and the Ensure unique solution checkbox instead. Board size is the ladder a buyer can see, so a title that bands its puzzles bands them by grid.
The other dial is Larger areas. It does something that surprises people: it cuts the clue count without changing the printed grid. A 7×7 at zero has a median of fourteen clues. Push the dial up and that falls away fast.
Here is the median and the middle 90% of 400 runs at each setting, which is a fairer picture than a handful of samples — the generator is random, and two runs at identical settings give different counts.
| Grid | Larger areas 0 | 0.5 | 1.0 | 2.0 |
|---|---|---|---|---|
| 7×7 | 14 (11–17) | 7 (6–8) | 4 (1–4) | 2 |
| 10×10 | 21 (16–26) | 11 (9–14) | 9 (8–11) | 4 (1–4) |
| 15×15 | 33 (26–42) | 21 (16–26) | 14 (11–17) | 9 (7–11) |
| 20×20 | 48 (37–61) | 28 (22–36) | 21 (17–26) | 11 (9–14) |
Two of those cells will publish a blank page. At 7×7 with the dial at 1.0, about 8% of boards come out as a single clue — one “49” on an otherwise empty grid. A 10×10 at 2.0 does the same thing at a similar rate. Those are not hard puzzles; they are not puzzles. Nothing warns you at generate time, so look at the run before a title goes near it.
One setting decides whether your book is honest. Ensure unique solution is ticked out of the box, and it is doing real work: untick it and the solver is skipped altogether, so the run can publish boards with more than one valid answer. If your cover says “one solution”, leave it alone.
Two more things before you write copy. On the Settings tab, Puzzle display offers Patches, and this is more than a change of font: it replaces the numeric clue with a shape glyph keyed to the rectangle’s orientation — square, wide or tall — so the solver is told the shape class and not the area. Everything above about a number being an area stops being true in that mode, which is a different promise to the buyer even though it is the same module. If you sell it, say what the glyphs mean. The shop name is Shikaku — the internal code name is Rectangles, but no shopper searches for that.
Galaxies — a dot is a center of rotation
Galaxies prints dots instead. The rule has three parts, and copy that drops any one of them describes a different puzzle. Every cell belongs to exactly one region. Each region contains exactly one dot. And each region looks the same after a half-turn about that dot.
Here is the part that catches people writing from memory. A dot is not always inside a cell. It can sit at a cell center, on the line between two cells, or on the corner where four meet. The region turns about whichever point its dot occupies. Across boards generated at four sizes and both difficulty settings, only about 42% of dots landed on a cell center. Another 39% sat on an edge and 19% on a corner. So a preview drawn as a tidy grid of centered pips is showing about two fifths of the real product.
Rows and columns run 7 to 15 and open at 10×10. Dot density barely moves with size. Measured across those runs it sits between one dot per four cells and one per five, drifting slightly sparser as the board grows — so a 10×10 carries about twenty to twenty-five dots and a 15×15 about forty to fifty-five.
Difficulty here is two named settings, Normal and Unreasonable, and nothing else. Normal is solvable by forced moves alone. Unreasonable needs bounded search. Both are solver-verified to have exactly one solution, so unlike Shikaku there is no way to ship an ambiguous board by accident. What the tiers do not do is change how the page looks: dot counts came out almost identical across both. So once again, the visible ladder in a title is board size.
Dots can be printed as your own images or as numbers instead of plain circles, both off by default. Neither changes the rule, so neither is a separate listing. Galaxies searches under two other names as well: Tentai Show and Spiral Galaxies.
What each listing has to show
The rule is the same for both, and it is not complicated: the sample has to be the puzzle the title names. A generic “logic puzzles” title drops you into the same results as sudoku, competing on nothing. The cover has to name the job — rectangles from numbers, or regions from dots. For how these two sit among other deduction types on Amazon, see logic puzzle books for KDP.
- KDP. Look Inside opens on the front of the book, so page one has to carry the clue type at readable size. Band the volume by grid: it is the one dial whose effect a shopper can see in a thumbnail, where clue density and a difficulty tier both look much the same.
- Etsy. The preview image has to match the file inside the ZIP — same grid size, same clue style, same look. If you sold Patches glyphs in the preview, the pack cannot be numerals. For how logic printables are usually sized and described on Etsy, start with Etsy logic puzzle printables.
- TPT. Put the answer key on its own page so a teacher can print class copies without it, and keep the board small — Shikaku opens at 7×7 and goes down to 4×4, and Galaxies bottoms out at 7×7 — so one sheet fits one lesson. Worksheet layout and answer-key habits for logic grids are covered in TPT logic puzzle worksheets.
Every paid Puzzle Maker Pro edition lets you sell the finished books, worksheets, and packs you make to your own readers and customers. Productivity adds the right to sell or supply the generated puzzles to other publishers and sellers.
The whole point
The two are close enough to confuse in a catalogue and nowhere near close enough to substitute in a listing. Shikaku’s difficulty lives entirely in grid size and clue density, and one unticked checkbox lets it publish puzzles with more than one answer. Galaxies cannot do that. It will, though, print dots on edges and corners that a hand-drawn preview never shows. Generate the run, look at what came out, and write the listing from that.
Other puzzles you might like
If you are still deciding between Shikaku, Galaxies, and Queens, the Galaxies vs Shikaku vs Queens comparison walks rules, settings, and two worked publishing scenarios. For the wider logic shelf on Amazon — loops, paths, region splits, and queens together — logic puzzle books for KDP maps where these modules fit. To see how region-split puzzles read in a mixed interior, mixing logic types in one KDP book explains when a collection title is honest and when it is not.