Normal sudoku rules apply. The sum of the digits on a line strictly between two circles is equal to a concatenation of the two values in the circles, in some order. For instance, 3_346_1 could be a valid split pea line, as 3+4+6=13, which is 1 concatenated with 3. A circled digit indicates exactly how many circles contain that digit. Note: This also includes all circles which are bounding the split pea lines. If, for example, a 3 appears in a circle, then there must be exactly 3 circles that contain a 3.