Normal sudoku rules apply.
A number outside the grid is the sum of all the digits between the 7 and the 8 in the corresponding row or column.
Pick any square with a 6 and the sum of all squares that are orthogonally adjacent to that square will always be 9.
Example:
On the left we see that the numbers between the 7 and the 8 adds up to 3.
At the bottom we see that all the numbers orthogonally adjacent to the 6 adds up to 9.
The puzzle:
solving online: penpa
Solution code: Row 3 from left to right, then row 8 from left to right. No gaps between numbers.
on 14. September 2020, 15:39 by Thorsby
Added a digit to make puzzle easier
on 24. August 2020, 12:54 by Lizzy01
You might like this: https://logic-masters.de/Raetselportal/Raetsel/zeigen.php?id=0003XE