Slingshot rules: If an arrow is present in a cell (here in the palindrome), the digit in the cell the arrow comes from appears in the grid in the direction of the arrow at a distance of N cells, where N is the digit in the arrow's cell. Other possible arrows are not given.
The two digits with the white point have a difference of 1.
Solution code: r7 and c8
on 1. October 2021, 22:52 by Vebby
Very nice!
For future solvers: Clarification of a rule in case of any confusion: Apart from its mirror on the other side of the palindrome, no digit can repeat on the palindrome; so on the length 15 palindrome, there will be 8 unique digits.
on 6. December 2020, 11:33 by stephane.bura
Great Slingshot puzzle :)
Thanks!