Some more Slovak Sums, see the previous one for the rules. This one is certainly more difficult.
Here’s another GP preview puzzle. It’s a bit degenerate, but maybe it’s still useful? For this type, there’s a bit more material out there:
- in the Mixed Bag round of the UK Open 2013
- in Matej Uher’s contribution to last year’s 24h puzzle championship
- a masterpiece by @pronter on twitter (now posted at Puzzle Graffiti including two smaller puzzles)
Rules Place digits from 1 to 4 in some blank cells, so that each row and column contains each digit exactly once. Clue numbers indicate the sum of orthogonally adjacent digits. The number of circles under a clue number indicates the number of digits involved in this sum. Or see the instruction booklet.