Creator of puzzles - Calcudoku 240 Hard Puzzles 8x8 (Volume 7)

Calcudoku (also known as "Mathdoku") is a mathematical and logical puzzle loosely similar to Sudoku.The objective is to fill the grid in with the digits 1 through N (where N is the number of rows or columns in the grid) such that: -Each row contains exactly one of each digit.-Each column contains exactly one of each digit.-Each bold-outlined group of cells (block) contains digits which achieve the specified result using the specified mathematical operation: addition (+), subtraction (-), multiplication ( ), and division ( ).-Unlike Killer Sudoku, digits may repeat within a block.