Normal sudoku rules apply. Draw a one-cell-wide loop of orthogonally connected cells. The loop may not touch itself, even diagonally. The loop acts as a German Whisper line, so all adjacent digits along the line must have a difference of at least 5. A (loopwich) clue outside the grid indicates the sum of the digits sandwiched between the first and last loop cell in their row or column. (Both loop and non-loop cells between the 2 ‘crust’ cells are summed)