I understand the whole hi-lo concept. (2-6= +1, 7-9= 0,10-A= -1). But how do casino's deal cards? I've heard they use two decks in blackjack (correct me if i'm wrong), but the only way I could see this method working is if after every round, the cards get discarded until eventually there are no cards left and the dealer shuffles all the 'old cards' thus making you have to start counting all over again. If this is the case, couldn't casino's completely ruin this whole system by just re-shuffling the deck after every round....?