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G22/R BACKGAMMON ROM Cartridge for the ZX Spectrum
Sinclair Research
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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 with pieces (also called 'men' or 'stones'), rather like draught pieces, and 
a pair of dice. A comparatively modern addition to the game 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 Z in the program. As the 
board is displayed, the black or red side is at the top, and the while or light 
blue side is at the bottom. The ZX Spectrum plays from the top side and owns the 
red men. 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 an 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 
precise 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, then you must play the higher throw.


Blocking

If a player has two of 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 it 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 provides 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 were 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 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 the program is loaded 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.

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.

You will then be asked whether you wish to enter your own die throws manually. 
Press Y for YES, or N key for NO. Press Y for YES only if you are convinced the 
program is cheating or you wish to play against another computer.

Once you have pressed N, the Backgammon table will then 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 (thus 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 settle in a double then 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 the 
same throw. When it is your move 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 3 categories:
1-Enter A to X to move a man from that point.
2-Enler Y to move a man off the bar.
3-Enler Z to play the other die first.

Provided that your move is legal, according to the rules of Backgammon, the 
appropriate man will be moved to its new post. 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 the 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 as 
moves.

After the Spectrum has played, you may double 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 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 doubting 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 OFFER - 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 
skilful 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 your 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.


Joysticks

You may not use joysticks with this game.