Logic Masters Deutschland e.V.

Another puzzle made after a snackdoku prompt from Scojo, but this one proved to be a bit above snack level and for that i was shamed into scrapping it altogether... but it's so cute. Hope you like a double doughnut as much as i do.

Inspired by the works of DubiousMobius.

• Normal 4x4 sudoku rules apply.
• The grid is a double torus: the edges of the grid are identified as the coloring indicates (for example, r3c1 is considered orthogonally adjacent to r4c4).
• Draw a closed loop through cell centers that doesn't cross itself, only moves orthogonally, and goes through all cells once except the cells marked with circles. The loop must cut the double torus into two disjoint surfaces, each one containing a circle. A cell marked with an arrow has a digit that counts the number of contiguous cells, including itself, that are part of the loop in that direction until the loop turns.

Online in Sudokupad (no loop solution check)

Online in Penpa+ (with loop solution check)