Hm... the intention was (if the basic mechanic is that AAA -> XBX) that AAAA -> XBBX and AAAAA -> XBBBX (which then cascades because of the three B in a row). Was something other than that happening for you, or are you referring to a different case?
And, based on some other comments, I'm actually feeling like an update might be in order... And among the improvements I have in mind is adding music that the cascades synchronize to ^_^
But anyway, thanks for the feedback!