# GRAVITY Instruction Booklet

## Instructions for GRAVITY

### Contents

Gravity Datapack
Gravity Standard Game Blank Sheets
Pencil, Rubber and Pencil Sharpener
Instruction Booklet

### The object of the game

The computer places a number of stars on a square board. The object of the game is to find and remove these stars in as few moves as possible, You find out where the stars are placed on the board by launching space probes into the board and watching where the probes come out. Each space probe you fire adds one to your score. The lower your score the better you have done.

### Rules of direction

There are five rules which govern the path space probes take through the board.

1. A space probe travels in a straight line unless it is deflected by a star.
2. When a space probe meets a star head on it is absorbed (or reflected straight back if the repulse option is chosen).
3. When a space probe meets the corner of a star it is deflected through 90 degrees away from the star.
4. When a space probe meets the corner of a star on the edge of the board it is deflected to trace a path around the outside of the board. It continues on its path around the edge of the board until it meets the corner of another star, at this point it emerges from the board.
5. Rule no. 2 (attraction / repulsion) has priority over rules 3 and 4 (deflection).

One consequence of these rules is that the path of a space probe is reversible. This means that if you launch a probe into the board at point 'a' and it emerges at point 'b', it will trace the same path if you reverse the procedure. That is if you launch a probe into the board at point 'b' it will emerge at point 'a'.

See Figure 1.

### THE RULES OF DIRECTION

Seed STANDARD 8 5 The Attract option was chosen.

### Getting started

Ensure that your Gravity Datapack is plugged in and that you have inserted GRAVITY into the top level menu.

From the menu call procedure GRAVITY.

Before you start to play there are some things you must tell the computer.

### The seed string

A random series of eight characters is displayed. This is the seed string. This string is used by the computer to generate the board. By making a note of the string you can play the same game again. You can change the string by using the ON/CLEAR key and typing in a new string (which must in eight characters).

### Board size

You are then asked for the size of the board. You may enter any number between 1 and 16. The computer will generate a square board of the size you specify.

### No. of stars

You must then specify the number of stars to be placed on the board.

### Hard copy

If you have anything in the top slot you will be asked whether you want a hard copy. See the section called 'Printing' below.

### Attract / Repulse

You will than be asked whether you wish to use the Attract or Repulse rule. See rule 2 in the 'Rules of direction' above.

### Playing the game

The gravity banner is then displayed. This consists of two miniature representations of the board.

ooo XXX ooo XXX

The left-hand side is used to show from which edge the space probe was launched and the right-hand side is used to show from which edge the space probe emerged.

### Launching a probe

You launch a space probe from the edge of the board. You specify which edge by using the keys:

8 - to launch from the top edge of the board
2 - to launch from the bottom edge of the board
4 - to launch from the left-hand edge of the board
6 - to launch from the rig ht-hand edge of the board

When you have chosen from which edge to launch the probe you then choose from which cell to make the launch. The cells are numbered from bottom to top and from left to right.

See Figure 1.

Note that if you change your mind at any stage when you are specifying information you can press the ON/CLEAR key which will let you back out of what you have started.

The best way to explain is by a few examples.

In all the examples which follow the game was set up as follows:

Seed STANDARD 8 5 The Attract option was chosen.

### Example 1

To launch a probe from the left-hand edge of the board at cell eight.

Press 4 (to indicate the left-hand edge.) At the In : prompt press 8 followed by EXE.

The display is as follows:

Xoo In : 8 ooX Xoo Out : 8 ooX

This indicates that the probe emerged at cell 8 on the right-hand edge of the board.

See Figure 1. Rule 1.

### Example 2

To launch a probe from the right-hand edge of the board at cell six.

Press 4 (to indicate the right-hand edge.) At the In : prompt press 5 followed by EXE.

The display is as follows:

Xoo In : 6 ooo Xoo Out : 0 ooo

This indicates that the probe did not emerge from the board.

See Figure 1. Rule 2.

### Example 3

To launch a probe from the top of the board at cell four.

Press 8 (to indicate the top of the board.) At the In : prompt press 4 followed by EXE.

The display is as follows:

XXX In : 4 ooX ooo Out : 7 ooX

This indicates that the probe emerged at cell 7 on the right-hand edge of the board.

See Figure 1. Rule 3.

### Example 4

To launch a probe from the left-hand edge of the board at cell three.

Press 4 (to indicate the left-hand edge.) At the In : prompt press 3 followed by EXE.

The display is as follows:

Xoo In : 3 ooX Xoo Out : 1 ooX

This indicates that the probe emerged at cell 1 on the right-hand edge of the board.

See Figure 1. Rule 4.

### Example 5

To launch a probe from the left-hand edge of the board at cell five.

Press 6 (to indicate the right-hand edge.) At the In : prompt press 5 followed by EXE.

The display is as follows:

ooX In : 5 ooo ooX Out : 7 ooo

This indicates that the probe did not emerge from the board.

See Figure 1. Rule 5.

### Removing a star

When you are confidant that you know where a star is you can take it off the board by trying a direct shot. You do this by pressing 5. You are then promoted to give the vertical and horizontal co-ordinates of the star. If you are correct the right-hand side of the banner shows 6 black squares. If you miss 6 white squares are shown and you are penalised by having points added to your score.

### Scoring

To complete the game you must find and remove all the stars from the board. The fewer points you score the better you have done.

1. Each launch you make adds one to your score. You may however repeat a shot with no penalty as long as the number of stars on the board has not changed. Note also that you are not penalised if you reverse a launch you have made (as long as the number of stars on the board has not changed).
2. If you take a direct shot (by pressing 5), then the star will be removed from the board if you hit it; this does not increase your score (successful shots are free). If you miss then the number of stars left on the board will be added to your score. You are not penalised twice if you make a direct shot twice on the same square.

### Ending the game

The game ends automatically when you have removed all the stars. The final screen shows you the seed string used and the number of points scored.

You can also end the game early by pressing the MODE key. This gives you four choices:

2. Select QUIT to end the game. You are shown the score and the seed string, but not the position of the stars. Press ON/CLEAR to quit.
3. Select PM (post mortem). This shows you the position of each star (press a key to set each one or ON/CLEAR to skip the rest), and finally the seed used and the points you have scored. Press ON/CLEAR to quit.

### Printing

If you wish to print you must have an RS232 or a COMMS Link attached to the top slot.

You can select print out at two stages.

1. After you have specified the size of the board and the star count you can print out blank board layouts on which to record the paths of your probes. To do this answer the prompts as follows:

Hard copy ? :

Reply N to ignore or Y to request hard copy print out.

To Console ? :

Reply N to send the data direct to the printer or Y to send a control Z (end of file) along with the data to be printed. This allows you to direct the print out to a printer via an IBM PC. To do this type:

copy com1 prn

at the 'A>' prompt on the PC and press RETURN before replying 'Y' to the 'To Console' prompt on the organiser. This is very handy if you don't have a serial port on your printer.

Copy Count ? :

Type a number between 1 and 99.

2. You may also print a copy of the board with the positions of the stars shown if you quit the game via the PM (post mortem) option. Simply answer the 'Hard Copy' and 'To Console' prompts as shown above.