Evolomino Puzzle Generator
Evolomino is a puzzle about shapes that evolve. You draw squares in the grid; squares joined side by side form blocks. Every block sits on exactly one arrow cell, every arrow passes through at least two blocks, and along each arrow each block is the one before it with one square added — same way round, never turned or flipped. This makes fresh puzzles at 5 or 6 squares a side, each with a single answer proved from the printed grid alone, and prints the puzzle and answer in black and white.
What this generator does
Lays out arrows, places a chain of growing blocks along each, and then prints as little as possible — blacked-out cells and the odd printed square — while one answer remains. Polyomino tiling puzzles fill a region with fixed pieces; here you must discover the pieces from how they grow.
How to use this tool
- Choose the grid size and press Make a puzzle. Add a puzzle code to make the same puzzle again.
- Draw squares on paper or a printout; blacked-out cells take no square.
- Press Show the answer: your squares are shaded grey, printed ones stay white.
Understanding the controls
- Grid
- 5 or 6 squares a side. 7 × 7 is not offered: in testing, proving one answer at that size usually ran past the search limit.
- Puzzle code
- Leave empty for a new puzzle from the browser's secure generator. With a code, the same code and size make the same puzzle again; the code is a seed, not a secret.
Worked examples
- Code harbour, 5 × 5
- 3 arrows of 3, 4 and 5 cells; 2 blacked-out cells and no printed squares; 9 squares in 6 blocks of 1 and 2.
- Code harbour, 6 × 6
- 4 arrows; 4 blacked-out cells and 1 printed square; 12 squares in 8 blocks.
Common use cases
- A shape-reasoning puzzle unlike number or shading puzzles
- Teaching translation versus rotation of shapes with a puzzle
- Printed sheets with answers
How this generator works
For each arrow the solver lists, in full, every chain of blocks it could pass through: a first block is any joined group of free cells holding exactly one arrow cell — every such group, of any size, is enumerated; no size limit is assumed — and each next block is a copy of the previous one with one square added, placed on a later cell of the same arrow without touching earlier blocks. Chains are then combined across arrows so that no two blocks overlap or touch and every printed square is covered. To make a puzzle, arrows are laid as random paths, a chain is drawn along each by the same listing in a shuffled order, every other cell starts blacked out, and squares are printed until one answer remains; blacked-out cells are then opened one by one, and printed squares removed, wherever one answer still remains. Every count shares one step limit; a count that reaches it proves nothing, and the change is not made. Afterwards blocks are found again from the answer by flood fill, each growth step is tested by removing every square of the larger block in turn, and the count is re-run from the printed grid.
Randomness and fairness
Arrows, the drawn blocks and the order in which clues are thinned come from a random sequence: the browser's secure generator, or a seeded one when you give a code. A code repeats a puzzle while the generator is unchanged. Codes are deterministic, not cryptographic.
For how randomness is produced across the whole site, see how Generate Random works.
Assumptions this tool makes
- Nikoli's published rules for Evolomino, restated on the page.
- Arrows never share a cell, as in Nikoli's examples.
Limitations and good to know
- 5 × 5 and 6 × 6 only.
- Evolomino puzzles here carry no difficulty grade; the number of arrows is not a measure of difficulty.
- Arrows are random paths, not designed; very easy puzzles do occur.
Common mistakes
- Rotating a block to make it fit
- The next block must contain the previous one the same way round. An L turned on its side is a different shape here.
- Leaving a block off every arrow
- Every block must cover exactly one arrow cell — a stray square anywhere else breaks the rules.
- Letting blocks touch
- Two blocks that touch side by side merge into one; keep a gap.
Practical tips
- Short arrows are the place to start: an arrow of three cells holds at most three blocks.
- The first block on an arrow is the smallest; often a single square at the tail.
- Blacked-out cells next to an arrow limit which way a block can grow.
Privacy and your data
Evolomino puzzles are built in your browser. With analytics consent, only the fact that a puzzle was made or failed is counted; the arrows, squares, answer and puzzle code are never sent.
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