Logic Masters Deutschland e.V.

It's just a normal Sandwich/Arrow sudoku, except it uses negative numbers. That should be pretty simple, right?

(in all seriousness, this shouldn't be too difficult... figuring out a notation system might be tricky though)

• Every row, column, and 3x3 box must contain all the numbers [-4, -3, -2, -1, 0, +1, +2, +3, +4] once each (IE, normal sudoku rules, but with the numbers -4 to +4 instead of the numbers 1 to 9).
• Sandwich Clues: Numbers outside the grid give the sum of the numbers sandwiched in between the -4 and the +4 in the indicated row or column.
• Arrow Clues: Numbers along an arrow must sum to the number in the circle. Numbers can repeat along an arrow, when allowed by other rules.

Penpa link: https://tinyurl.com/4axdbhsr

NOTE: For Penpa's answer check, use the Sudoku number tab, and color the negative cells gray.