Normal sudoku rules apply. The 3x3 boxes are numbered in normal reading order. Each digit matching its box number is an "inoculation site". Each row and column contains an inoculation site. They are infected. Infected cells infect every orthogonally adjacent cell with a smaller digit. Infections keep spreading until no infected cell has a smaller uninfected orthogonal neighbour. (Every infected cell can be traced back to one or more inoculation sites.) All uninfected cells form one orthogonally connected area. Each orthogonally connected group of infected cells touches the grid's edge. A digit in a blue circle is uninfected and counts the number of infected cells in its 8 surrounding cells. Green lines connect 2 infected digits that differ by 5 or more. Pink dots join consecutive uninfected digits.