Hydrogen
(Published on 11. August 2026, 08:00 by Kaktuslav)
Rules: Normal sudoku rules apply.
Circles and pluses: Place nine circles in the grid: one in each row, column, and 3×3 box, with the circled cells forming a complete set of the digits 1–9. A digit in a cell containing a plus equals the sum of two summands: the circled digit in its row and the circled digit in its column.
Solution code: Row 9, with the circled digit in brackets, e.g. 123(4)56789
Comments
yesterday, 15:03 by puzzlepandit
Interesting concept and nice flow.
on 16. August 2026, 14:18 by Rabarberkalle
Nice. A bit tricky at first but once you grasp the concept it was quite easy from there.
on 15. August 2026, 15:06 by Agent
Great puzzle, some fresh logic and fun to solve!
on 13. August 2026, 08:01 by Crusader175
Very nice!
on 12. August 2026, 20:21 by greebug
Another beauty from Kaktuslav!
on 12. August 2026, 15:38 by highonlife
This is easily over 3* in difficulty. Close to 4.
Really beautiful concept though.
on 12. August 2026, 15:37 by highonlife
This is easily over 3* in difficulty. Close to 4.
Really beautiful concept though.
on 12. August 2026, 15:28 by amirs
Once I understood the rules, the puzzle became very smooth and fun. Before that I was shaking my head wondering how it could ever be 2*...
on 12. August 2026, 02:54 by Snookerfan
Very nice, I did not solve it the 2 star way I guess, thanks for the challenge!
on 12. August 2026, 01:25 by pmays123
This one was very tough for me to get into the right mindset, but I really enjoyed it. Great challenge. Thanks for sharing!
on 11. August 2026, 19:24 by marcmees
Great puzzle fun. 3*imo. Thanks
on 11. August 2026, 17:38 by GeorgeTheToad2
Thank you Kaktuslav for a lovely puzzle that was a treat to solve. I would agree with a 2* difficulty if you can see how to start otherwise it becomes more difficult.
on 11. August 2026, 15:25 by Kaktuslav
Clarifying that each plus corresponds to a sum of two digits.
on 11. August 2026, 13:13 by Dogfood
Loved it as always. Definitely 2* once I approached it right. Good lunch break snack.
on 11. August 2026, 11:38 by sujoyku
Awesome puzzle! I found it much harder than 2 stars, but I enjoyed it mightily. Thank you, Kaktuslav!
