Fill the grid so each row and column uses every number once, and keep every arrow between the cells true.
A Latin square with opinions. The signs do most of the work once you learn to read them in chains.
Click a cell and type a number, or use the pad beside the board. Each row and each column has to hold every number from one up to the grid size, exactly once.
The arrows between neighbouring cells point at the smaller of the two. An arrow is a rule, not a hint, so a grid that breaks one is wrong even if every row and column looks fine.
Anything that contradicts a row, a column or a sign turns red as soon as you place it, so you are never hunting for where things went wrong.
A few numbers are given to start. Harder grids are bigger and start you with less, leaning more on the signs.
At the smaller number, always. A sign between two cells reads as a less than or greater than between them, exactly as it would in arithmetic.
Find the longest chain of signs all pointing the same way. On a five wide grid a chain of three forces the ends immediately, because only the smallest and largest numbers can sit at the extremes of a run that long.
Yes. Clues and signs are taken away only for as long as a single answer survives, so a puzzle never needs guessing.
There are no boxes, the grids are smaller, and the inequality signs replace most of what the boxes would have told you. It tends to feel tighter, with less bookkeeping and more deduction per square.
Futoshiki comes from Japan, and the name means unequal, which is about as direct as a puzzle name gets. It reached a wider audience when British newspapers began running it in the mid 2000s, alongside the sudoku boom.
The grid is a Latin square, a shape mathematicians have studied for centuries and which turns up in experiment design and error correcting codes. The inequality signs are what turn a filing exercise into a puzzle.
Good solvers barely write numbers down at first. They read the signs, work out which cells can only be the smallest or the largest, and the rest of the grid tends to follow from there.