Backgammon
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Backgammon is a great game - easy to learn, fast, exciting, a perfect
blend of chance and skill. This high quality Backgammon program uses fast
and efficient machine code to choose its moves. Full feature game including
graphics board, rolling dice and rolling cube. You will need more than
just luck to win against your ZX SPECTRUM.

Backgammon is a 3000 year old game of chance and skill for two people - or
in this case between a computer and a person. The game is played on a
special backgammon board which pieces (also called "men" or "stones"),
rather like draught pieces, and a pair of dice. A comparatively modern
addition to the games is the doubling cube which gives the game an extra
dimension and enhances the opportunity of using skill rather than just luck
to defeat one's opponent.


The Backgammon Board:
The board consists of 24 points which are divided into four "tables" each
consisting of 6 points. The points are represented by alternative white and
black triangles and are denoted by the 24 letters from A to X in the
program. As the board is displayed, the black or red side is at the top and
the white or light blue side is at the bottom. The ZX SPECTRUM plays from
the top side and owns the red men and you play on the bottom side using
the light blue men. The thick vertical black area which divides the board
is called the bar. The two tables to the right of the bar are the inner
tables and the two tables on the left are the outer tables.

The Rules of Backgammon:

The Play:
Your men play with the alphabet (from right to left at the top and from
left to right at the bottom) and the ZX SPECTRUM'S red men move in the
opposite direction.

The Objective:
Your objective is to move all your men into your inner table (points S to X)
and then to bear them off the table before the ZX SPECTRUM does the same
thing with his men and his inner table (points A to F).

The Move:
You and the ZX SPECTRUM take turns to roll the dice and move one or more men
the precice number of spaces indicated by the dice. Each die must be played
individually and each move must be legal. If a double is thrown then the
value of the throw is doubled and four separate and individual moves must
be made. If you can play only one die or only the other then you must play
the higher throw, and you msu play both throws if possible.

Blocking:
If a player has two or more men on a point then that point is blocked to his
opponent. His opponent may not land on that point, even temporarily.

Hitting:
If a player has only one man on a point (a blot) then his opponent can land
on that point and send the man to the bar - this is called a hit.

The Bar:
If a player has one or more men on the bar then he must move them off the
bar before he makes any other play. If you are on the bar then you will come
in (unless you are blocked) as if you had men on a point immediately to the
right of point A. Similarly the ZX SPECTRUM will come off the bar as if he
had men on a point immediately to the right of point X. A player who cannot
get off the bar may lose a part or all of his turn.

Bearing Off:
When a player has all his men in his inner table then he can start bearing
off. If a throw bears off exactly, i.e. the man would land exactly one
point past the last point then that man can be borne off. A man can also
be borne off with a throw that is too high provided that that man is the
furthest man out.

The Doubling Cube:
At the beginning of the game, the doubling cube is at the centre of the bar
and shows either 64 (which really indicates 1) or 2. While the doubling
cube is so placed, either player has the right to offer his opponent a
double. A player who wishes to offer a double (because he believes that
he is likely to win the game) must make the offer at the start of his own
turn, before rolling his dice. If his opponent declines this offer then he
loses the game and the offerer wins the number of points displayed on the
doubling cube before the offer was made. If the offer is accepted then the
doubling cube is turned to the next highest number and placed nearest to the
player who accepted the double. That player then has charge of the cube and
only he can subsequently offer another double (which he might want to do
if the game where to turn in his favour) in which case the doubling cube
and the right to offer a double would change hands.

Scoring:
The first player to bear off all his pieces wins at least the number of
points displayed on the doubling cube. If the loser has not borne off any
men but does not have a man on the bar or on his opponent's home table then
the win is a gammon and the winner collects double the number of points
shown on the doubling cube. If the loser still has a man on the bar or on
his opponent's inner table then the win is a backgammon and the winner
collects three times the number of points shown on the doubling cube.


Playing the ZX Spectrum:

If you are not familiar with the rules of Backgammon, you can learn them
as you play since the program will not let you make an illegal move and it
will also tell you why a move is illegal.

After loading the program, you will be asked a couple of questions. First
you will be asked for the level of ZX SPECTRUM play: press 1 to 4, where 4
is the hardest level. You will then be asked whether you wish to enter your
own die throws manually. Press Y for YES, or N for NO. Press Y for YES only
if you are convinced the programme is cheating or you with to play against
another computer (see bottom for the randomness of the dice).

Having set the level of play the score will be displayed along with the
current level of ZX SPECTRUM play. You will be given an opportunity to go
back  to the first page (press Y for yes) or play a game (press N for no).
If you do not respond within 40 seconds the program will enter an
automatic demonstration mode.

Once you have pressed N, the Backgammon table will be displayed and the dice
will roll to decide who will play first. The doubling cube in the middle of
the bar is set at 64 which really indicates 1 (this may seem strange but
traditionally there is no 1 on a doubling cube and 64 is used to indicate
both 1 and 64). If the rolling dice setting in a double the stake (as
indicated by the doubling cube) will be doubled to 2 and the dice will be
rolled repeatedly until a non-double is thrown. Your die is on the top:
whoever has the highest throw plays first with that same throw.

When it is your modve and the dice have settled, the program will prompt
you with the message.

YOUR MOVE WITH THE n

where n is the number on one of the die. You reply by entering a single
letter which falls into three categories:

1 - Enter A to X to move a man from that point.
2 - Enter Y to move a man off the bar.
3 - Enter Z to play the other die first.

Provided that your move is legal, according to the riles of Backgammon, the
appropriate man will be moved to its new point. If your move is illegal, a
message informing you why the move is illegal will be flashed up and you
will be asked for your move again. If you cannot move, the program will tell
you so and then pass to the ZX SPECTRUM'S turn.

When you have pressed the key or keys to make your move(s), you may still
change your mind by deleting and re-entering your moves. To replay your
moves, press the DELETE key ("0") on your Spectrum. This will return your
man to its previous position. You may then press a key to make a new move.
When you are satisfied with your moves, press ENTER to complete your moves
and allow the Spectrum to make its moves.

After the Spectrum has played, you may doule by pressing the key D. If you
do not wish to double, press ENTER to roll your dice. If the ZX SPECTRUM
accepts the offer of a double, the number the number on the doubling cube
will double and the cube will move over to the ZX SPECTRUM'S side. Pressing
D has no special effect if the ZX SPECTRUM has charge of the doubling cube.

If the ZX SPECTRUM does have charge of the doubling cube, then it may offer
you a double before it rolls the dice with the prompt:

DOUBLE OFFERED - Y TO ACCEPT

If you enter Y to accept, then the number on the doubling cube will double
and the cube will move over to your side. If you press any other key to
reject, the Spectrum will ask for confirmation that you are resigning.
Press R to resign. The game will terminate with the ZX SPECTRUM winning the
current stake as displayed on the doubling cube.

Backgammon is a game of both skill and luck. It is not unusual for the less
skillful player to win the odd game by having more luck. If you want to
compare your play with that of the ZX SPECTRUM you should play a series of
games for points. You would normally play a reasonable number of games if
you play "first to eleven", i.e. the winner is the first to accumulate
eleven points.

At any stage of the game when it is you turn to move, you may ask the
Spectrum to recommend a move by pressing the key "1".

The rolling of the dice is guaranteed to be completely random. It uses the
random number generator which is continuously called while you are
thinking of your move and frozen by the random time at which your move
is entered.

Made in U.K.
(C) Copyright 1983 Psion Ltd.

(Transcribed by Robin Stuart)
