Place the digits 1 to 9 once each into each row, column and region. Regions need to be deduced by the solver and consist of 9 orthogonally-connected cells. For each blue line, digits on the line have an equal sum N within each region the line passes through. If a line passes through the same region more than once, each individual segment of such a line within that region sums to N separately. Every line must enter at least two regions. A digit in a circle indicates the number of digits on that particular segment of the line within that region. Not all circles are necessarily given.