Gattai-3
Gattai is a Japanese word meaning merged or fused; this term is used for overlapping sudoku. A number after the word "Gattai" indicates how many 9 x 9 sudokus are in the puzzle .
Sudokus that no one can solve
Sudokus that no one can solve, not only including Sodukus which is very difficult but also that no one trying to solve it.