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
(ocultar) ¡Juega una partida en tiempo real contra un adversario conectado! Tan sólo debeís seleccionar por defecto la acción "Mover y permanecer aquí" y ¡recargar la página con la tecla F5! (TeamBundy) (mostrar todos los consejos)