Logic Masters Deutschland e.V.

This is a variant of the sandwich sudoku which I haven't seen before. I called it Pocket Sandwich Sudoku. I hope you'll like it :)

Rules: Place the digits 1-9 exactly once in each row, column and 3x3 block. Additionally:
A digit in a circle in the first column indicates the sum of the digits placed between 1 and 9 in the corresponding row.
A digit in a circle in the first row indicates the sum of the digits placed between 1 and 9 in the corresponding column.
A digit in a square in the first column indicates the difference between the highest and lowest digit placed between 1 and 9 in the corresponding row.
A digit in a square in the first row indicates the difference between the highest and lowest digit placed between 1 and 9 in the corresponding column.
Squares and circles may contain 1 or 9.

This puzzle is also available on Penpa.

Enjoy solving! :)