The game of "SET"

The game of set consists of a deck of 81 cards, which represents
one each of all possible combinations of these attributes:

		Shape:		Diamond		Oval		Squiggle
		Colour: 	Red			Blue		Green
		Texture:	Clear		Shaded		Solid
		Number:		One			Two			Three

At any given time, the game displays a selection of cards on the
screen, and the challange is to be the first to recognize a "set"
of cards.

A "set" of cards is defined as any three cards, in which for EACH
of the above attributes, they are either "All the Same", or "All
Different". For example, cards in a set will have either all the
same shape, or all different shapes. If two cards have the same
shape, and the third is different, then they are NOT a set. This
criteria must be applied to EACH of the four attributes - if any
single attribute is the same on two cards and different on the
third, then the cards are NOT a set.

Up to nine players may participate. When you think you have identified
a set, press the keyboard digit corresponding to your number (1-9).
The screen will clear (so you can't hit your key and then look for a
set), and you will be asked to enter the three letters which identify
the cards in your set.

If you think there are no more sets, press 'C' to deal another card.
Press 'D' to reshuffle and redeal the deck.
Press 'S' to show a list of the sets currently on the screen.
Press ' ' to redraw the display (after Show)
Press ESC to end the game.
