They’re Quadruples even when they don’t contain four digits, because they still give information about four cells. Right? Let’s go with that. These Quadruples clues contain only one or two digits, but to make up for that, I’ve put a quadruple of Quadruples into each 3x3 box. With 36 Quadruples clues, I think they don’t really need more digits.
Rules:
Normal Sudoku rules apply.
Digits within circles appear at least once in cells touching the circle.
Estimated difficulty: 2 out of 5
Solve on SudokuPad