This puzzle is essentially a Latin square with addition. All you really need to know is how to add single-digit numbers, although subtraction is also useful. Once you’ve spend a few minutes sorting out which numbers mean what, you’re ready to start puzzling!

Can you figure out the rules from the solved puzzle?

Screenshot 2014-07-22 19.07.43

Once you’ve mastered these, you might enjoy creating your own puzzles: just start with the tick and X-marks, work out the sums, then decide how many of the sums to give as clues.

I think this puzzle was invented by Otto Janko.  Check out his website for this and many other intriguing games.

Here is another on-line Kakurasu generator.  Although the site is in Polish. it’s pretty self-explanatory!