I'm not sure that anybody recognized it, but my last 2 sudokus were totally same.
First I made the Product Sudoku that I found a bit hard. So I change the clues into Quadruple, and I published it. But it was solved so quickly, so I tried the original version, too.
It's intresting that the product version is 8x harder.
Today sudoku is based on my Mastertrio puzzle which appeared on the WPC2011.
I can't determine its difficulty, but it's tend to be hard.
I hope you will enjoy it.
Rules for Secret Code Sudoku
Standard sudoku rules apply. Moreover find out the 4-digit secret code. Digit repeting is allowed in the code and the order of digits is not relevant. Some intersection contain a smallnumber. Each small number denotes the number of digits around it that are part of the code.
For instance if the code 1,3,3,4 and the number 3,4,4,7 has 2 matches: 3 and 4 are common.