Summary: A shaped Slitherlink is a normal Slitherlink puzzle with one twist: when the solver closes the loop, it outlines a letter, a digit, a drawing or a silhouette. This guide shows how to pick the shape source on the Shape tab, type letters, draw or trace your own shape in the editor, use silhouette images, and export the puzzle with its shaded solution.
Overview
In a regular Slitherlink the loop is random. On the Shape tab you can make the loop outline something instead: a letter or digit from the built-in Block set, a shape you draw in the editor, or a silhouette image. The puzzle page looks like any other Slitherlink and the clue digits still say how many loop segments border each cell. As in every picture puzzle, the pattern of clues gives an attentive solver a hint of what is coming; the shape itself appears, stroke by stroke, as the loop closes. Treat it as the reward for finishing, not a secret. The solution page shades the inside of the loop so the answer key shows the shape at a glance.
That makes shaped loops a natural fit for alphabet and number books, themed collections (a heart for Valentine’s Day, a house, a fish, a leaf) and hidden-message books where each puzzle reveals one letter of a word. New to Puzzle Maker Pro? Read How Puzzle Maker Pro Works for the Preview, Create and book workflow first, then come back here for the Shape tab.
Required Modules
Puzzle Maker Pro – Slitherlink — product page: Puzzle Maker Pro Slitherlink.
- Lite makes Slitherlink puzzles on the rectangular grid, exports JPG, PNG, SVG and PDF, and includes Instant Puzzle Books (a book PDF from your current settings) and Puzzle Book Studio (one collection, full book editing). Creative adds the other 17 grid shapes and the shaped loops this tutorial is about: letters and digits, drawn shapes and silhouette images. Productivity adds Time Saver, Puzzle Book Studio Productivity (books that combine several collections) and JSON export. You can move up to a higher edition later, so start with the one that fits what you are making today. See Puzzle Maker Pro Editions Explained.
- Commercial rights: Lite and Creative both carry the licence to sell the finished puzzle products you make — books, worksheets and printable packs — to your own readers and customers, including KDP, Etsy and Teachers Pay Teachers. Productivity adds the right to sell or supply the puzzles themselves to other publishers and sellers.
A free demo is available, so you can try Slitherlink before you buy: try the free demo. The demo makes the regular random-loop puzzle as a watermarked image; the Shape tab unlocks with Creative.
Preparation
Open Puzzle Maker Pro, choose Slitherlink, and go to the Settings tab first. Shaped loops are drawn on the square grid, so keep Grid type on Rectangular; on any other grid type the module draws a random loop and says so in the notice strip. Set Rows and Columns between 3 and 15 (a larger value is brought down to 15 for shapes). A letter needs at least 9 rows and 7 columns and the module raises a smaller board to that size for you. The default 8 × 8 is fine to start: letters come out on a 9-row by 8-column board, drawings bring their own size, and silhouettes use the board you set. A 9 × 9 to 13 × 13 board is the sweet spot: large enough for the shape to read, small enough to solve in one sitting.
When you pick a shape source, the Difficulty drop-down is greyed out and labelled (not used for shaped loops): the shape fixes the loop, and the generator strips the clues a solver does not need while keeping exactly one solution. Boards up to 13 per side come out at a medium level and 14 or 15 per side at an easy one, so keep one book within one of those ranges for a consistent feel.
Pick the Shape Source
Open the Shape tab. The Loop shape drop-down has four entries:
- Random loop — the regular Slitherlink you already know.
- Letters and digits (Block) — type letters and digits; each puzzle outlines one of them.
- Drawn shapes (editor) — draw, type or trace a shape in the grid editor.
- Silhouette images — pick image files or built-in silhouettes.
The hint under the drop-down reads “The solved loop outlines the shape; the solution shades the inside. Square board only, no difficulty setting.” Pick a source and the matching controls appear below it. One rule holds for all three sources: each entry in your list makes one puzzle, in order, and Quantity cycles through the list (a larger quantity starts again from the first entry, a smaller one stops early).
Type Letters and Digits
Choose Letters and digits (Block) and type into the box labelled Letters (one puzzle each, A-Z 0-9). Spaces are ignored and lower case is fine: abc and A B C both give A, B and C.
- One puzzle per character. Type
HELLO, set Quantity to 5, and you get H, E, L, L, O in that order, ready for a page sequence that spells the word. For an alphabet book type the 26 letters once, set Quantity to 26, and click Create: one run, no batch tooling needed. - A-Z and 0-9 only. The letters come from Block, a built-in letter set designed so that every character is a single closed outline. Any other character, such as
&oré, stops the run with a message naming it, so the batch never silently skips a page. - Letters with holes are stencilled. A, B, D, O, P, Q, R and the digits 0, 4, 6, 8 and 9 keep a one-cell gap from each hole to the outside, the way a stencil does (B and 8 have two), because one closed loop cannot enclose a hole. The letters stay recognisable and the puzzle stays a single loop.
A letter is always drawn at the same size, 5 cells wide and 7 tall, and centred on the board with at least a one-cell margin, so a bigger board gives the shape more empty grid around it rather than a bigger letter. A 9 × 9 to 11 × 11 board keeps the letter prominent.
Draw Your Own Shape
Choose Drawn shapes (editor). The Designs (one puzzle each) list works like the letters box. New… opens the editor on a blank grid of 9 rows by 7 columns, Edit… reopens a design, Clear drops it.
The editor is titled Draw a loop shape. The left mouse button paints the inside of the loop, the right button erases, and the badge above the grid tells you at every stroke whether the drawing is usable: One loop ✓ in green, or in red what is wrong, such as 1 hole or 2 pieces, 1 corner touch. Three rules decide it, and each has a reason in the puzzle:
- One piece. Two separate blobs would need two loops, and a Slitherlink has exactly one.
- No holes. A hole inside the shape would be a second, inner loop.
- No corner-only touches. Two cells that meet only at a corner would make the loop cross itself at that corner, which the rules forbid.
Four tools help you get there fast:
- Name and Size — the name appears in your puzzle list and in any message about the design; Size sets the grid from 3 × 3 to 15 × 15 and Resize applies it. A design brings its own board size, so a 12 × 10 drawing makes a 12 × 10 puzzle whatever the Settings tab says.
- Text — type a character, pick a font and optionally Bold or Italic, then click Trace. Block heads the font list and traces one letter or digit straight into a valid loop; an installed font traces any short text as that typeface’s outline, a starting point you then tidy with the brush and Make loopable until the badge turns green.
- Import image… — loads a picture onto the grid as a starting trace, for a shape you already have as a file.
- Make loopable — one click repairs the drawing: it keeps the largest piece and drops any smaller separate pieces, then fills holes and joins corner touches by adding cells. Join the pieces you want to keep with a brush stroke first, then click. A traced font letter usually needs just this one click. The button is active whenever the badge is red and something is drawn.
Click OK to save the design. The module uses a design exactly as drawn: if a saved design is not one loop, its puzzle reports the badge sentence instead of generating, so fix it in the editor where you can see it.
Use Silhouette Images
Choose Silhouette images, then fill the list with Add … for your own image files or Add built-in … for the shipped silhouette set: circle, heart, star, diamond, cross, arrow, crescent, egg, house, flower, fish, leaf, cat, apple and spade. That set maps neatly onto a school or holiday calendar: egg for spring, leaf for autumn, star and crescent for winter, heart for February. Delete, Clear, Shuffle and the arrow buttons manage the order.
A silhouette is converted to cells on the board you set on the Settings tab, so Rows and Columns decide how much detail survives. Bold, connected silhouettes on a plain background work best: the module keeps the largest piece, fills enclosed pockets and thickens thin diagonal joins so that one loop can outline the picture, and lists what it changed in the notice strip at the bottom of the Slitherlink panel. A picture that keeps too few cells on the chosen board reports that in the same strip and asks for a bolder picture or a bigger board; one that fills the whole board asks for a picture with some background. Raise Rows and Columns towards 15 for a detailed silhouette; drop to 9 or 11 for a simple one like the heart.
Colour the Shaded Solution
On the Style tab, Loop shape fill sets the colour that shades the inside of the loop on the solution image. The default is a very light grey; for a black-and-white or cream book interior choose a mid grey so the shape survives the press, and print one proof page before a full run. Pick a tint if your solutions are in colour. Only the solution page is shaded. The usual Slitherlink lines are all still yours: Shapes (the cell outlines), Dot and Solution Line, plus the canvas and puzzle border. See How to Customize Puzzle Designs in Puzzle Maker Pro for the shared controls.
Set the Title
On the Titles tab, choose a Smart Title. Slitherlink offers:
- Slitherlink GridSize — e.g. “Slitherlink 9×9”
- Slitherlink GridType — e.g. “Slitherlink Rectangular”
- Slitherlink Difficulty — e.g. “Slitherlink Normal”
- Grid Size — e.g. “9×9”
- Grid Type — e.g. “Rectangular”
- Difficulty — e.g. “Normal”
- Slitherlink GridSize Difficulty — e.g. “Slitherlink 9×9 Normal”
- Custom — your own title text
For shaped puzzles Slitherlink GridSize or Custom reads best: a title that names the letter would spoil the reveal, and shaped puzzles have no difficulty of their own. The same options are available for the puzzle Description, whose default is “Draw a single loop through all clues”. See How to Create Smart Puzzle Titles in Puzzle Maker Pro for how the mechanism works.
Generate and Export
Click Preview to see the first puzzle and its solution, then Create to generate the full quantity. The notice strip at the bottom of the Slitherlink panel lists anything worth knowing about the run: a silhouette that was adjusted, a design that still needs Make loopable, or a character the Block set has no glyph for. Export as JPG, PNG, SVG or PDF: the puzzle page is the worksheet, the shaded solution is the answer key. Send the collection to Puzzle Book Studio for a finished book, or, when one book mixes several sources or sizes, queue a row per source in Time Saver (Productivity), each row holding its own letters, designs or silhouettes.
Outcome
You can now make Slitherlink puzzles whose solved loop reveals a letter, a digit, a shape you drew, or a silhouette, with the solution shaded so the answer key shows the shape at a glance. One run of 26 letters gives you an alphabet book; a list of silhouettes gives you a themed collection; a typed word spread over a page sequence gives you a hidden message the reader uncovers one puzzle at a time.
FAQ
Can the loop spell a whole word in one puzzle?
No, one puzzle outlines one character, because every character is its own closed loop and a Slitherlink has exactly one. Type the word in the letters box and set Quantity to its length: each puzzle reveals the next letter, and the word appears across the sequence.
Why do letters like A, B and O have a gap in them?
A closed loop cannot enclose a hole, so the Block set draws every letter with a hole as a stencil: a one-cell gap connects the hole to the outside. The letter stays readable and the puzzle stays a single loop.
Which edition do I need for shaped loops?
Shaped loops, letters, drawn shapes and silhouettes alike, are a Creative feature; Lite makes the regular random-loop Slitherlink on the rectangular grid. You can move up from Lite to Creative or Productivity later. For an alphabet book, Creative with Quantity 26 is enough; Time Saver (Productivity) is for mixing sources and sizes in one run.
Can I use a shape on a hexagonal or Penrose grid?
Shaped loops are drawn on the rectangular grid. Keep Grid type on Rectangular on the Settings tab for any shape source, and use the other 17 grid shapes for random loops.
Can the solver see the shape before solving?
Partly: the clue digits cluster along the outline, so an attentive solver can guess the general shape, as in any picture puzzle. The letter or picture itself appears only as the loop is drawn, and the shading is on the solution page alone.
Does a drawing have to fit the board size on the Settings tab?
No. A design brings its own size from the editor, from 3 × 3 to 15 × 15, and the puzzle uses that. Letters and silhouettes use the Rows and Columns from the Settings tab, with letters raised to at least 9 × 7.