The solver is given a 9x9 grid, partially divided by black cells into compartments. Each compartment, vertically or horizontally, must contain a straight – a set of consecutive numbers, but in any order. For example: 7, 6, 4, 5 is valid, but 1, 3, 8, 7 is not. Like sudoku, the solver must fill the remaining white cells with numbers 1 to 9 (or 1 to n in puzzles with N cells per side) such that each row and column contains unique digits. Whereas Sudoku has the additional constraint of 3x3 boxes, in Str8ts rows and columns are divided by blacks cells. Additional clues are set in some of the black cells – these numbers remove that digit as an option in the row and column. Such digits do not form part of any straight.