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Learning to count cards is much easier than Hollywood or the casinos would have
us believe.  Some systems only require you to track a single running total in
your head.

One such system, called the Knock-out system of card counting, is extra easy. 
You start your count at 4 - (4 x number_of_decks).  That gives us an initial
running count of 0, -4, -20, or -28 for the common casino shoe sizes of 1, 2, 6,
or 8 decks.  From there, you add one each time you see a 2, 3, 4, 5, 6 or 7 and
subtract one when you see a 10, jack, queen, king, or ace.  The 8 and 9 cards do
not affect the count.  Once you learn to track the running count, you can make
strategy decisions and vary your bets based on the times when the count is in
your favor.

That's not a lot to remember, but it does take practice to get fast.  You really
need to get to where you can count a deck in 20 to 30 seconds if you are going
to keep up with those fast moving casinos dealers.

This week's Ruby Quiz is to build a training program for helping you learn to
count cards.

The program needs to show you one or more cards at a time, running through a
Blackjack shoe.  As it goes, the program should track the running count.  Have
it pause at random intervals, ask you the count, and notify you if you are right
or wrong.

Both the time to go through the deck and the number of cards displayed at a time
should be configurable.  It's important to practice with seeing multiple cards
at once because you learn to cancel out pairs of high and low cards.  It might
even be nice to provide a mixed mode, which varies the number of cards shown at
a time.

You can show cards as simple Strings, ASCII art, or full graphics as you prefer.
You may wish to make cards fully disappear after their display time though, to
make the conditions more like they would be in a casino.