Animal Word Search

The two shortest names are what breaks a word search

FOX and BAT are three letters each, and three letters happen by accident. Fill the gaps of a finished grid with random letters from the same alphabet and some of those gaps will spell a listed word a second time, somewhere the puzzle knows nothing about. The effect is not small: 600 grids across every theme on this site, filled that naive way, produced 33 boards carrying a second copy of a listed word, roughly one in eighteen, and BAT appeared in every worked example. Somebody who circles that copy is right and the board says no, which is the worst thing a puzzle can do.

So the gaps are not filled at random. A letter goes into one cell at a time and is kept only if it completes no listed word running through that cell in any of the eight directions, and the whole grid is then scanned once more from scratch. If that scan still finds a second reading the fill is thrown away and done again, up to six times; if the board still will not come clean it is rebuilt from nothing, up to eight times. When even that fails the page says it could not build a grid, which costs one reload, instead of handing over a puzzle that cannot be finished.

Thirteen of the twenty-five, and never the same thirteen

The board is thirteen wide and hides thirteen words, so twelve mammals sit out each time and the choice is shuffled again on every load. That matters more than it sounds. The obvious way to choose is longest first, because long words are the hard ones to fit, and a generator that does it that way hides the same eleven names on every single board and never once hides FOX or BAT. DEER, MOLE, SEAL, VOLE, HARE, LYNX and MINK would go the same way. Here the shuffle picks the thirteen first, and only then sorts those thirteen longest-first so they pack.

No animal on this list contains another

That is a rule about the list rather than about the grid, and it exists because circling the smaller word inside a larger one is a correct find that the puzzle would have to reject. So the list carries DEER and no compound built on it, and it never pairs a word with something that swallows it whole.

The same rule kills a word and its own reverse, and that one bites hardest. Hide STAR and RATS and you have hidden one run of four cells twice over: only one of the two can ever be credited to a drag, the other is refused every time it is found, and the board can never be completed. Whichever of such a pair comes second is dropped before the grid is built.

Why the word search animals list is all British mammals

The theme was compiled for this site rather than lifted out of a dictionary, because a themed grid only works if the words belong together: a dictionary can hide twenty-five words in a square but it cannot make them a subject. Every name here is a mammal that lives wild in Britain, spelled the British way, and a name has to be at least three letters long and no longer than the board is wide before it can be hidden at all.

Two entries are two words, PINE MARTEN and WILD BOAR. A grid has no cell for a space, so the space comes out before placement and PINEMARTEN goes down as ten letters in a row, while the list printed beside the grid keeps the space, because that is how the name is written. At ten letters it is the longest thing on the list and the first word placed whenever it is drawn: the longest word has the fewest places it will fit, so it goes down while the grid is still empty and the short ones bend around it. Neither compound is a rarity, either: thirteen of the twenty-five go onto every board, so each of the two turns up on about half of them.

This board runs at the middle setting, which is four of the eight directions: along a row to the right, straight down a column, and the two diagonals that also travel rightwards. One of those two descends and the other climbs, so a name can run upwards here even though nothing on the board is written backwards – every word still begins at its leftmost letter. Backwards words live on the fifteen-wide grid.