Miroslav Balac is engineer of technology who spent his career innovating and designing. He was a Technical Director in one of the major companies in Energy and Oil industry, but was also a teaching assistant at University, lead project director etc. Wherever he worked, he always left something new and worthwhile behind. He constructed a novel type of puzzle, a DDT puzzle (in several different variations). This is an apparently impossible puzzle and, of course, it can be solved. He is the author of the books: “SUDOKU: Don”t Do That” and “Mystery of Sudoku” (trilogy).