SudoKanard

Determinant Sudoku Classic Sudoku rules apply. Each number in a square is the determinant of the underlying 2×2 array, i.e. the result of the operation [(top left) times (bottom right)] minus [(top right) times (bottom left)]. Solve on Penpa: https://tinyurl.com/26xu7ly5

 No Touch Sudoku Standard Sudoku rules apply. Any two cells sharing a corner must contain different digits. Solve on Penpa: https://tinyurl.com/y6jz8at4 Solve on SudokuPad:  https://tinyurl.com/2abn6888

 Killer/Quadruples Sudoku Standard Sudoku rules apply. Killer : the digits in a cage must sum to the number printed in its corner; digits may not repeat within a cage. Quadruples : circled digits where four cells meet must be present as values in those four cells. Solve on Penpa: https://tinyurl.com/22685wop Solve on SudokuPad:  https://tinyurl.com/y4uw5arv

 Irregular Sudoku Place a digit from 1 to 9 in each cell. Each column, each row and each outlined region must contain every digit once. Solve on Penpa: https://tinyurl.com/y3gvvymm Solve on SudokuPad: https://tinyurl.com/2acphwsk