Here is a variant that hasn't appeared much (maybe at all?) on Logic Masters Germany which has a really simple and enjoyable ruleset.
Rules
Normal sudoku rules apply. Every row, column and box must contain the digits from 1-9.
Normal quadruple sudoku rules apply. Digits in a circle must appear at least once in the four surrounding cells.
Normal X sudoku rules apply. Each of the marked diagonals must contain the digits 1-9.
As always, your comments and ratings are very much appreciated. I hope you enjoy!
Lösungscode: Rows 2 and 8
am 28. April 2024, 04:12 Uhr von Willy Wonka
Updated online solving links
am 31. Januar 2023, 13:13 Uhr von ForzaFcu
amazing puzzle. very nice
am 6. August 2020, 03:17 Uhr von Narayana
@emmettcito ditto!
am 5. August 2020, 22:44 Uhr von SudokuExplorer
What a lovely puzzle! It was really enjoyable! :-)
am 4. August 2020, 23:17 Uhr von glum_hippo
Quite rewarding!!
am 4. August 2020, 20:05 Uhr von aneoid
Challenging (for me at least) and extremely rewarding; thanks, WW.
am 4. August 2020, 07:18 Uhr von Richard
There is only one other (plain and full) quadruple: 00022P
As far as I know of.