Fill a grid so every animal, shape or number appears once in each row and column. Five levels from 4 by 4 zoo grids to 6 by 6 with thick boxes.
A Latin square is a grid where each symbol appears exactly once in every row and exactly once in every column. In a 4 by 4 zoo grid the symbols are four animals, so each row has a frog, a cat, a dog and a rabbit in some order, and so does each column. Some squares are already filled in, and the child fills in the rest. The skill is elimination, which is the most useful single idea in logic puzzles and contest problems. A child looks at an empty square, asks which animals are already in its row and its column, and crosses them out in their head. When only one animal is left, that square is certain. Then that animal helps to rule things out somewhere else. This is reasoning from rules to a sure answer instead of guessing, and it carries over to maths, reading and games like chess.
Level 1, One to find, is a 4 by 4 animal grid with a single empty square, so a 6-year-old can win on the first day by looking along one row. Level 2, Animal rows, hides five to seven animals. Level 3, Shape detective, uses stars, moons, hearts and suns, hides nine or ten squares and leaves only six or seven shown, so the child has to chain several certain squares together. Level 4, Number grid, is a 5 by 5 grid of the numbers 1 to 5 with fourteen to sixteen squares empty. Level 5, Boxed grid, is 6 by 6 with the numbers 1 to 6, twenty-two to twenty-four squares empty, and a third rule: the grid has thick lines that cut it into six boxes of two rows by three columns, and each box must hold every number once as well. The top levels are hard for age 6 and 7 and are best done with a pencil and a parent next to the child.
The game first builds a complete grid by backtracking with the symbols tried in random order, so the finished grid is a valid Latin square (there are 576 different ones at 4 by 4). Then it hides squares one at a time in random order. After each hide, a solver searches for completions and counts them, stopping at two. If exactly one completion remains, the square stays hidden. If a second completion appears, the square is put back. In this game that check is stricter: a square may only be hidden if a person could still finish the whole grid by two plain moves, never by trying options. Move one: a square where only one symbol fits, because the others are already in its row, column or box. Move two: a symbol that has only one empty place left in a row, column or box. The generator runs both moves like a person would and keeps the puzzle only if they fill every square, on every level including the top one. So every puzzle has exactly one answer, and no guessing is needed. The check button accepts any full grid that keeps all the rules and keeps the squares that were shown, and with a single completion that is the same answer. The tests repeat the count with a second, separate solver on 500 puzzles at every level, and also check that boxes on level 5 really are enforced.
A printed worksheet has 4, 6 or 8 new grids at the level you pick, on Letter or A4 paper, with an answer key on the last page. The PDF is made in your browser and nothing is uploaded. The game has no timer, no lives and no ads in the play area, and a wrong try only shakes the square. This page does not teach times tables or reading, and it does not go beyond 6 by 6. It also does not use clues like greater-than signs: every puzzle is solved by the one rule of once per row, per column, and on level 5 per box.
A square grid in which every symbol appears once in each row and once in each column. A 4 by 4 grid with four animals is a Latin square when no animal repeats in any row or column.
Yes. Every puzzle is checked by a solver so exactly one completion exists. Each puzzle is built so that two plain moves always fill the whole grid: find a square where only one symbol fits, or a symbol that has only one empty place left in a row, column or box (and on level 5, in a thick box). The game checks this on every puzzle, so there is always a next square that is certain.
Ages 6 to 8. Level 1 has one empty square. Level 3 on a 4 by 4 grid and levels 4 and 5 with numbers are for a child who likes challenges, ideally with a parent.
A 6 by 6 grid is divided into six boxes of 2 rows by 3 columns. Each box must also hold the numbers 1 to 6 once, which gives extra clues so that few starting numbers still leave one answer.
Yes. Choose a level, 4, 6 or 8 grids and Letter or A4. Each worksheet is new and the filled-in grids are on the last page.
No. Puzzles are made in your browser, and stars and level stay on this device. The page counts visits with Google Analytics, never answers or grids.