What is card counting?

Card counting is keeping track of one thing: the ratio of high cards to low cards still left in the shoe. Every card that is dealt changes what remains, and the count compresses all of that into a single number you can carry in your head.

It works because the two halves of the deck are not equal. High cards — tens and aces — favour you: more blackjacks paid at 3:2, stronger doubles, and a dealer who busts more often when forced to draw on a stiff hand. Low cards favour the dealer. When the cards still to come are rich in tens, the edge quietly flips from the house to you.

What it is not: memorising every card, or any kind of trick. The Hi-Lo count is a running tally of +1 and −1, and the maths behind it was published by Edward Thorp in 1962. It is legal everywhere; a casino may still ask a winning counter to leave, because it is their house.

At the table it comes down to four habits: keep the count, convert it to a true count, bet more when it is positive, and change a handful of plays. Everything else is plain basic strategy. The Speed Drill in this trainer builds the first of those habits until it runs on its own.