Str8ts facts for kids
Str8ts is a logic-based number-placement puzzle, invented by Jeff Widderich in 2008. It is distinct from, but shares some properties and rules with Sudoku. The name is derived from the poker straight. The puzzle is published in a number of newspapers internationally, in two book collections, and in downloadable apps. It was featured on the Canadian television show Dragons' Den on November 24, 2010.
Gameplay
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.
There are a number of variants to the basic game, including Symmetric Str8ts, Asymmetric Str8ts, Mini-Str8ts, and Transformations.
Grading
As Str8ts belongs to the same class of puzzles as Sudoku the puzzle can demonstrate a wide spectrum of relative difficulty. The grade is determined by a combination of opportunities to solve at each stage and the difficulty of the strategy that grants each solution. An easier puzzle will have many places where a logical deduction can place a solution or eliminate a candidate number. When the whole puzzle is assessed in this way, plus some heuristics, a score can be determined. Over a large number of puzzles (>10,000) a bell curve of scores can be produced. This can be quartiled to group puzzles into specific grades.
