Normal sudoku rules apply. In each row, column and 3x3 box are two 'crusts'. All nine 1s are crusts, as well as nine other cells, which could be any digit. The clues outside the grid give the sum of the digits between the two crust cells in that row or column. The capsules contain the coordinates of each of the nine crust cells that are not 1s. No two capsules refer to the same crust cell.