EMPIRE(6)

NAME
empire - the wargame of the century

SYNOPSIS

empire [-w water] [-s smooth] [-d delay] [-S save-interval] [-f savefile]

DESCRIPTION

Empire is a simulation of a full-scale war between two emperors, the computer and you. Naturally, there is only room for one, so the object of the game is to destroy the other. The computer plays by the same rules that you do.

-wwater
    This option controls the amount of water on the map. This is given as the percentage of the map which should be water. The default is 70% water. water must be an integer in the between 10 and 90 inclusive.

-ssmooth
    This controls the smoothness of the map. A low value will produce a highly chaotic map with lots of small islands or lakes. A high value will produce a map with a few scattered continents. Be forewarned that a high value will cause the program to take a long time to start up. The default value is 5.

-ddelay
    This option controls the length of time the computer will delay after printing informational messages at the top of the screen. delay is specified in milliseconds. The default value is 2000 which allows the user two seconds to read a message.

EXAMPLES

empire -w90 -s2

This produces a map with many islands.

empire -w50 -s0

This produces a really strange map. These values are not recommended for the faint at heart.

empire -w10

This produces a map with lots of land and a few lakes. The computer will have a hard time on this sort of map as it will try and produce lots of troop transports, which are fairly useless.

There are two other option.

-Sinterval
    sets the save interval for the game (default is 10). Once per interval turns the game state will be automatically saved after your move. It will be saved in any case when you change modes or do various special things from command mode, such as `M' or `N'.

-fsavefile
    Set the save file name (normally empsave.dat).

INTRODUCTION

Empire is a war game played between you and the computer. The world on which the game takes place is a square rectangle containing cities, land, and water. Cities are used to build armies, planes, and ships which can move across the world destroying enemy pieces, exploring, and capturing more cities. The objective of the game is to destroy all the enemy pieces, and capture all the cities.

The world is a rectangle 60 by 100 squares on a side. The world consists of sea (.), land (+), uncontrolled cities (*), computer-controlled cities (X), and cities that you control (O).

The world is displayed on the player's screen during movement. (On terminals with small screens, only a portion of the world is shown at any one time.) Each piece is represented by a unique character on the map. With a few exceptions, you can only have one piece on a given location. On the map, you are shown only the 8 squares adjacent to your units. This information is updated before and during each of your moves. The map displays the most recent information known.

The game starts by assigning you one city and the computer one city. Cities can produce new pieces. Every city that you own produces more pieces for you according to the cost of the desired piece. The typical play of the game is to issue the Automove command until you decide to do something special. During movement in each round, the player is prompted to move each piece that does not otherwise have an assigned function.

Map coordinates are 4-digit numbers. The first two digits are the row, the second two digits are the column.

PIECES

The pieces are as follows:
Piece | You | Enemy | Moves | Hits | Str | Cost
Army | A | a | 1 | 1 | 1 | 5(6)
Fighter | F | f | 8 | 1 | 1 | 10(12)
Patrol Boat | P | p | 4 | 1 | 1 | 15(18)
Destroyer | D | d | 2 | 3 | 1 | 20(24)
Submarine | S | s | 2 | 2 | 3 | 20(24)
Troop Transport | T | t | 2 | 1 | 1 | 30(36)
Aircraft Carrier | C | c | 2 | 8 | 1 | 30(36)
Battleship | B | b | 2 | 10 | 2 | 40(48)
Satellite | Z | z | 10 | -- | -- | 50(60)

The second column shows the map representation for your units.

The third shows the representations of enemy units.

Moves is the number of squares that the unit can move in a single round.

Hits is the amount of damage a unit can take before it is destroyed.

Strength is the amount of damage a unit can inflict upon an enemy during each round of an attack.

Cost is the number of rounds needed for a city to produce the piece.

The number in parenthesis is the cost for a city to produce the first unit.

Each piece has certain advantages associated with it that can make it useful. One of the primary strategic aspects of this game is deciding which pieces will be produced and in what quantities.

Armies can only move on land, and are the only piece that can move on land. Only armies can capture cities. This means that you must produce armies in order to win the game. Armies have a 50% chance of capturing a city when they attack. (Attacking one's own city results in the army's destruction. Armies that move onto the sea will drown. Armies can attack objects at sea, but even if they win, they will drown.) Armies can be carried by troop transports. If an army is moved onto a troop transport, then whenever the transport is moved, the army will be moved with the transport. You cannot attack any piece at sea while on a transport.

Fighters move over both land and sea, and they move 8 squares per round. Their high speed and great mobility make fighters ideal for exploring. However, fighters must periodically land at user-owned cities for refueling. A fighter can travel 32 squares without refueling. Fighters are also shot down if they attempt to fly over a city which is not owned by the user.

Patrol boats are fast but lightly armored. Therefore they are useful for patrolling ocean waters and exploring. In an attack against a stronger boat, however, patrol boats will suffer heavy casualties.

Destroyers are fairly heavily armored and reasonably quick to produce. Thus they are useful for destroying enemy transports which may be trying to spread the enemy across the face of the world.

When a submarine scores a hit, 3 hits are exacted instead of 1. Thus submarines can inflict heavy damage in a fight against heavily armored boats. Notice that healthy submarines will typically defeat healthy destroyers two-thirds of the time. However, a submarine will defeat a fighter about two-thirds of the time, while a destroyer will defeat a fighter three-fourths of the time.

Troop transports are the only pieces that can carry armies. A maximum of six armies can be carried by a transport. On any world containing a reasonable amount of water, transports will be a critical resource in winning the game. Notice that the weakness of transports implies they need protection from stronger ships.

Aircraft carriers are the only ships that can carry fighters. Carriers carry a maximum of the number of hits left of fighters. Fighters are refueled when they land on a carrier.

Battleships are similar to destroyers except that they are much stronger.

Satellites are only useful for reconnaissance. They can not be attacked. They are launched in a random diagonal orbit, and stay up for 50 turns. They can see one square farther than other objects.

All ships can move only on the sea. Ships can also dock in a user-owned city. Docked ships have damage repaired at the rate of 1 hit per turn. Ships which have suffered a lot of damage will move more slowly.

Because of their ability to be repaired, ships with lots of hits such as Carriers and Battleships have an additional advantage. After suffering minor damage while destroying enemy shipping, these ships can sail back to port and be quickly repaired before the enemy has time to replenish her destroyed shipping.

The following table gives the probability that the piece listed on the side will defeat the piece listed at the top in a battle. (The table assumes that both pieces are undamaged.)
 | AFPT | D | S | C | B
AFPT | 50.0% | 12.5% | 25.0% | 00.391% | 00.0977%
D | 87.5% | 50.0% | 25.0% | 05.47% | 00.537%
S | 75.0% | 75.0% | 50.0% | 31.3% | 06.25%
C | 99.6% | 94.5% | 68.7% | 50.0% | 04.61%
B | 99.9% | 99.5% | 93.8% | 95.4% | 50.0%

Notice, however, that when a ship has been damaged, the odds of being defeated can go up quite a bit. For example, a healthy submarine has a 25% chance of defeating a battleship that has had one hit of damage done to it, and a healthy submarine has a 50% chance of defeating a carrier which has suffered two hits of damage.

MOVEMENT FUNCTIONS

There are a variety of movement functions. The movement functions of pieces can be specified in user mode and edit mode. Cities can have movement functions set for each type of piece. When a movement function for a type of pieces is set for a city, then every time that type of piece appears in the city, the piece will acquire that movement function. Be forewarned that moving loaded transports or loaded carriers into a city can have undesirable side effects.

Normally, when a movement function has been specified, the piece will continue moving according to that function until one of the following happen:

    • An enemy piece or unowned city appears next to the piece. In this case the piece will be completely awoken, unless its movement function has been set to a specific destination. Armies on ships and pieces inside cities will not be awoken if the enemy piece is gone by the time it is their turn to move.

    • You explicitly awaken the piece.

    • The piece can no longer move in accordance with its programmed function. In this case, the piece will awaken temporarily. You will be asked to move the piece at which time you may awaken it.

    • The piece is a fighter which has just enough fuel (plus a small reserve) to get to the nearest city. In this case, the piece will awaken completely, unless its movement function has been set to a specific destination, or its movement function has been set to land.

The rationale behind this complexity is that fighters must be awoken completely before they are out of range of a city to prevent one from accidentally forgetting to waken the fighter and then watching it fly off to its doom. However, it is presumed that when a path is set for the fighter, the fighter is not in danger of running out of fuel.

Pieces do not completely awaken when their function has been set to a destination because it is slightly time consuming to reset the destination, but very simple (one keystroke) to wake the piece.

The movement functions are:

Attack
    This function applies only to armies. When this function is set, the army will move toward the nearest enemy city, unowned city, or enemy army. This is useful when fighting off an invading enemy or taking over a new continent. When an army is set to this mode, it will also explore nearby territory. This tends to make the "grope" movement mode pretty useless.

Awake
    When pieces are awake, you will be asked for the direction in which the piece should move on each turn.

Fill
    This function applies to carriers and transports. When this function is specified, these ships sleep until they have been filled with fighters or armies respectively.

Grope
    This function causes a piece to explore. The piece heads toward the nearest unseen square of the map on each of its moves. Some attempt is made to explore in an optimal fashion.

Land
    This function applies to fighters and causes the fighter to head toward the nearest transport or carrier.

Random
    This movement function causes a piece to move at random to an adjacent empty square.

Sentry
    This movement function puts a piece to sleep. The function of a city cannot be set to 'sleep'.

Transport
    This movement function only works on armies. The army sleeps until an unfull transport passes by, at which point the army wakes up and boards the transport.

Upgrade
    This movement function only works with ships. The ship will move to the nearest owned city and remain there until it is repaired.

<dir>
    Pieces can be set to move in a specified direction.

<dest>
    Pieces can be set to move toward a specified square. In this movement mode, pieces take a shortest path toward the destination. Pieces moving in accordance with this function prefer diagonal moves that explore territory. Because of this, the movement of the piece may be non-intuitive.

As examples of how to use these movement functions, typically when I have a new city on a continent, I set the Army function of the city to attack. Whenever an army is produced, it merrily goes off on its way exploring the continent and moving towards unowned cities or enemy armies or cities.

I frequently set the ship functions for cities that are far from the front to automatically move ships towards the front.

When I have armies on a continent, but there is nothing to explore or attack, I move the army to the shore and use the transport function to have that army hop aboard the first passing transport.

COMMANDS

There are three command modes. The first of these is "command mode". In this mode, you give commands that affect the game as a whole. In the second mode, "move mode", you give commands to move your pieces. The third mode is "edit mode", and in this mode you can edit the functions of your pieces and examine various portions of the map.

All commands are one character long. The full mnemonic names are listed below as a memorization aid. The mnemonics are somewhat contrived because there are so few characters in the English language. Too bad this program isn't written in Japanese, neh?

In all command modes, typing "H" will print out a screen of help information, and typing <ctrl-L> will redraw the screen.

COMMAND MODE

In command mode, the computer will prompt you for your orders. The following commands can be given at this time:

Automove
    Enter automove mode. This command begins a new round of movement. You will remain in move mode after each of the computer's turns. (In move mode, the "O" command will return you to command mode after the computer finishes its next turn.

City
    Give the computer a random unowned city. This command is useful if you find that the computer is getting too easy to beat.

Date
    The current round is displayed.

Examine
    Examine the enemy's map. This command is only valid after the computer has resigned.

File
    Print a copy of the map to the specified file.

Give
    This command gives the computer a free move.

J
    Enter edit mode where you can examine and change the functions associated with your pieces and cities.

Move
    Enter move mode for a single round.

N
    Give the computer the number of free moves you specify.

Print
    Display a sector on the screen.

Quit
    Quit the game.

Restore
    Restore the game from empsave.dat.

Save
    Save the game in empsave.dat.

Trace
    This command toggles a flag. When the flag is set, after each move, either yours or the computer's, a picture of the world is written out to the file 'empmovie.dat'. Watch out! This command produces lots of output.

Watch
    This command allows you to watch a saved movie. The movie is displayed in a condensed version so that it will fit on a single screen, so the output may be a little confusing. This command is only legal if the computer resigns. If you lose the game, you cannot replay a movie to learn the secrets of how the computer beat you. Nor can you replay a movie to find out the current positions of the computer's pieces. When replaying a movie, it is recommended that you use the -d option to set the delay to around 2000 milliseconds or so. Otherwise the screen will be updated too quickly for you to really grasp what is going on.

Zoom
    Display a condensed version of the map on the screen. The user map is divided into small rectangles. Each rectangle is displayed as one square on the screen. If there is a city in a rectangle, then it is displayed. Otherwise enemy pieces are displayed, then user pieces, then land, then water, and then unexplored territory. When pieces are displayed, ships are preferred to fighters and armies.

MOVE MODE

In move mode, the cursor will appear on the screen at the position of each piece that needs to be moved. You can then give commands to move the piece. Directions to move are specified by the following keys:

            QWE
            A D
            ZXC

The arrow and keypad keys on your terminal, if any, should also work.

These keys move in the direction of the key from S. The characters are not echoed and only 1 character is accepted, so there is no need for a <Return>. Hit the <Space> bar if you want the piece to stay put.

Other commands are:

Build
    Change the production of a city.

Fill
    Set the function of a troop transport or aircraft carrier to fill.

Grope
    Set the function of a piece to grope.

Idir
    Set the direction for a piece to move.

J
    Enter edit mode.

Kill
    Wake up the piece. If the piece is a transport or carrier, pieces on board will not be awoken.

Land
    Set a fighter's function to land.

Out
    Cancel automove mode. At the end of the round, you will be placed in command mode.

Print
    Redraw the screen.

Random
    Set a piece's function to random.

Sentry
    Set a piece's function to sentry.

Transport
    Set an army's function to transport.

Upgrade
    Set a ship's function to upgrade.

Vpiece func
    Set the city movement function for the specified piece to the specified function. For example, typing "VAY" would set the city movement function for armies to attack. Whenever an army is produced in the city (or whenever a loaded transport enters the city), the army's movement function would be set to attack.

Y
    Set an army's function to attack.

?
    Display information about the piece. The function, hits left, range, and number of items on board are displayed.

Attacking something is accomplished by moving onto the square of the unit you wish to attack. Hits are traded off at 50% probability of a hit landing on one or the other units until one unit is totally destroyed. There is only 1 possible winner.

You are "allowed" to do fatal things like attack your own cities or other pieces. If you try to make a fatal move, the computer will warn you and give you a chance to change your mind.

You cannot move onto the edge of the world.

EDIT MODE

In edit mode, you can move around the world and examine pieces or assign them new functions. To move the cursor around, use the standard direction keys. Other commands are:

Build
    Change the production of the city under the cursor. The program will prompt for the new production, and you should respond with the key corresponding to the letter of the piece that you want produced.

Fill
    Set a transport's or carrier's function to fill.

Grope
    Set a piece's function to grope.

Idir
    Set the function of a piece (or city) to the specified direction.

Kill
    Wake all pieces at the current location. If the location is a city, the fighter path will also be canceled.

Mark
    Select the piece or city at the current location. This command is used with the "N" command.

N
    Set the destination of the piece previously selected with the "M" command to the current square.

Out
    Exit edit mode.

Printsector
    Display a new sector of the map. The map is divided into ten sectors of size 20 by 70. Sector zero is in the upper-left corner of the map. Sector four is in the lower-left corner of the map. Sector five is in the upper-right corner, and sector nine is in the lower-right corner.

Random
    Set a piece to move randomly.

Sentry
    Put a piece to sleep.

Transport
    Set an army's function to transport.

Upgrade
    Set a ship's function to upgrade.

Vpiece func
    Set the city movement function for a piece.

Y
    Set an army's function to attack.

?
    Display information about a piece or city. For a city, the production, time of completion of the next piece, movement functions, and the number of fighters and ships in the city are displayed.

Note that you cannot directly affect anything inside a city with the editor.

HINTS

After you have played this game for a while, you will probably find that the computer is immensely easy to beat. Here are some ideas you can try that may make the game more interesting.

    • Give the computer one or more extra cities before starting the game.

    • Try playing the game with a low smoothness value (try using the -s2 or even -s0 option).

    • When starting the game, the program will ask you what difficulty level you want. Here "difficulty level" is a misnomer. To compute a difficulty level, the program looks at each continent and counts the number of cities on the continents. A high "difficulty level" gives the computer a large continent with many cities, while the user gets a small continent with few cities. A low "difficulty level" has the opposite effect. It may be the case that the computer will play better when the "difficulty level" is low. The reason for this is that the computer is forced to move armies to multiple continents early in the game.

HISTORY

According to A Brief History of Empire[1], the ancestral game was written by Walter Bright sometime in the early 1970s while he was a student at Caltech. A copy leaked out of Caltech and was ported to DEC's VAX/VMS from the TOPS-10/20 FORTRAN sources available sometime around fall 1979. Craig Leres found the source code on a DECUS tape in 1983 and added support for different terminal types.

Ed James got hold of the sources at Berkeley and converted portions of the code to C, mostly to use curses for the screen handling. He published his modified sources on the net in December 1986. Because this game ran on VMS machines for so long, it has been known as VMS Empire.

In 1987 Chuck Simmons at Amdahl reverse-engineered the program and wrote a version completely in C. In doing so, he modified the computer strategy, the commands, the piece types, many of the piece attributes, and the algorithm for creating maps.

The various versions of this game were ancestral to later and better-known 4X (expand/explore/exploit/exterminate) games, including Civilization (1990) and Master of Orion (1993).

In 1994 Eric Raymond colorized the game.

FILES

empsave.dat
    holds a backup of the game. Whenever empire is run, it will reload any game in this file.

empmovie.dat
    holds a history of the game so that the game can be replayed as a "movie".

BUGS

No doubt numerous.

The savefile format changed incompatibly after version 1.13.

Satellites are not completely implemented. You should be able to move to a square that contains a satellite, but the program won't let you. Enemy satellites should not cause your pieces to awaken.

AUTHORS

Original game by Walter Bright. Support for different terminal types added by Craig Leres. Curses support added by Ed James. C/Unix version written by Chuck Simmons. Colorization by Eric S. Raymond. Probability table corrected by Michael Self.

COPYLEFT

Copyright (C) 1987, 1988 Chuck Simmons

See the file COPYING, distributed with empire, for restriction and warranty information.

NOTES

1.  A Brief History of Empire
    http://www.classicempire.com/history.html