# vim:ft=txt #. Proximity analysis - some cells can be eliminated because they are not reachable (also consider that white cells of certain islands interfere with the extent of different islands). #. A straight row or column of black cells can be tested for black cells in its middle which will place two white cells and so one can conclude that they are white. #. If you have something like: |[B][G][B] |[G][G][B] ----------------- Then it is evident that the upper [G] (Gray/Unknown) has to be white, or else the lower [G]s will also all be black. #. Cells between two islands (either diagonally or in a one-cell spacing) must be black, or else the two islands will be joined. #. Filling-style strategy: if past a certain geometery (that is within the limits of its number), an island can only expand into one cell, then that cell will be white. #. If an Island reaches certain points that reaching them consumes all of its number, then its white edge points can be marked with black in the opposite direction to its extent.