Giant: Twenty-five 5×5 regions. 100×100 – Sudoku-zilla. 100 10×10 regions. Variants with additional or different constraints Sudokus variants can also have additional constraints on the placement of digits, such as "< >" relations, sums, linked cells, etc. Hypersudoku – Additional 3×3 boxes are added within the main grid. Main diagonals unique – The cell values along both main diagonals must be unique, such as Sudoku X. Relative digit location – Digits use the same relative location within selected regions. The matching cells or regions are often color-coded. Killer sudoku (clue sums) – Regions of various shapes and sizes. The usual constraints of no repeated value in any row, column or region apply. The clues are given as sums of values within regions (e.g. a 4-cell region with sum 10 must consist of values 1,2,3,4 in some order). Sandwich sudoku - numbers outside the grid specify the sum of the digits in a row or column which are sandwiched between the '1' and the '9'. Terms related to solving The meanings of most of these terms can be extended to region shapes other than boxes (square-shaped). To simplify reading, definitions are given only in terms of boxes. Scanning – The process of working through a puzzle to look for or eliminate values. Cross hatching – Process of elimination that checks rows and columns intersecting a block for a given value to limit the possible locations in the block. Counting – Process of stepping through the values for a row, column or block to see where they can or cannot be used. Box line reduction strategy – A form of intersection removal in which candidates which must belong to a line can be ruled out as candidates in a block (or box) that intersects the line in question. Candidate – Potential value for a cell. Contingency – A condition limiting the location of a value. Chain – A sequence of contingencies connected by alternative values. Higher circuits – Related locations outside the immediate row, column and grid. The locations are related by value contingencies. Independent clues – A set of clues that cannot be deduced from each other. Often depends on the order of choosing the clues for a given grid. Intersection removal – When any one number occurs twice or three times in just one unit (or scope) then that number can be removed from the intersection of another unit. For