Normal sudoku rules apply. Shade some additional cells grey ("walls") and leave some unshaded ("cave"). The cave is one orthogonally-connected group, and walls form orthogonally-connected groups that touch an edge of the grid. Draw a 1-cell wide loop that moves orthogonally, entering every cave cell (and no wall cells). Each digit on the loop in row N differs from its neighbours on the loop by at least N. Gold is found in wall cells with digits larger than their row number. All possible gold has been given. Digits separated by a white dot have consecutive values.