Without looking at the game, i will assume that the last move filled the bottom row, making it dissappear and everything else drop down. The blue square is to indicate the last move was in that column. It is very possible to have several moves in the same square (in the bottom row only) because of this rule. Hope that helps!
Kevin
(dölj) Om du vill hålsa på någon på deras eget språk, prova då Spelarnas Ordlexikon, vid länken "mer om språk" under flaggorna. (pauloaguia) (Visa alla tips)