This manual describes the internals of Enigma (http://www.nongnu.org/enigma/), in particular how to build new levels using Lua and how to interact with the game engine. It describes Enigma version 0.90.

Introduction
************

This chapter explains how Enigma works internally and how you can create your own levels.  This manual is not for users of graphical level editors, but rather for programmers of graphical level editors or users who want to use the full power of the Enigma ``engine'' by using the built-in scripting language.

There are two kinds of file formats you can use to build levels for Enigma.  The traditional solution was to write small programs in a programming language called Lua.  Although this is still possible, the preferred way is now to prepare files in a data-centric format called XML; this will be discussed in detail in chapter

Enigma's level format is extremely flexible and allows you to create very dynamic and interactive levels.  Here are a few examples of levels that make heavy use of Lua, both when preparing the level and during the game:

  * Flood Gates (nat8.lua) Was one of the first levels to use Lua for more than simply building the level and then handing it over to the game engine.  The flowing water is controlled by a small function written in Lua--there is no built-in suppport for flowing water in the game engine.

  * Enigris (ralf04.lua) lets you play Tetris inside Enigma.

  * Mourning Palace (ant08.lua) moving platforms, also controlled by a Lua function.

  * Finally, some of the maze levels and most of the levels in the Sokoban pack are dynamically generated: They look a little different every time you play them.

Our focus is on using Lua to access Enigma's game engine, so you won't learn much about Lua as a language in this chapter.  Many simple things, like function calls or if statements, will appear familiar to anyone having a little programming experience: In many ways Lua is similar to programming languages like Basic or Pascal.  But for most of Lua's finer points you will have to reach for the official Lua documentation, which you can download from lua.org (http://www.lua.org).

Creating New Levels
===================

Creating a new level basically consists of the following steps

 1. Writing the level description, for example a file named daniel01.lua.

 2. Inserting the new level into a level pack of your choice

 3. Creating a preview image for the level

 4. Testing the level in Enigma

A Simple Level
==============

Here is a very simple level description that can also serve as a starting-point for new landscapes.  (In fact, this is the first level in Enigma, so you can try it out right away.)

      1   CreateWorld(20, 13)
      2   draw_border("st-brownie")
      3   fill_floor("fl-hay", 0,0, level_width,level_height)
      4
      5   set_stone("st-fart", level_width-1,0, {name="fart"})
      6   set_stone("st-timer", 0,0, {action="trigger", target="fart",
      7             interval=10})
      8
      9   oxyd(3,3)
     10   oxyd(level_width-4,level_height-4)
     11   oxyd(level_width-4, 3)
     12   oxyd(3,level_height-4)
     13   oxyd_shuffle()
     14
     15   set_actor("ac-blackball", 10,6.5)

The resulting level looks like this inside the game:

Let's now turn to a line-by-line analysis of this program:

      1   CreateWorld(20, 13)
      2   draw_border("st-brownie")
      3   fill_floor("fl-hay", 0,0, level_width,level_height)

The level begins with a call to CreateWorld, which creates a new world that is 20 blocks wide and 13 blocks high.  Every block in the world can be accessed with a pair of coordinates: The upper left corner has coordinates (0,0), the lower right one has coordinates (19,12).  Every block contains a floor tile, an (optional) item, and an (optional) stone.

A frame of stones is drawn around the newly created landscape with the draw_border command.  Its argument, "st-brownie", is the name of a stone.  By convention, all stones have "st-" prefixed to their name, similarly all item names begin with "it-" and all floor names with "fl-".

The fill_floor command in line 3 fills the complete floor with tiles of type "fl-hay".  The other arguments are the upper left corner and the width and height of the rectangle to be filled.

      5   set_stone("st-fart", level_width-1,0, {name="fart"})
      6   set_stone("st-timer", 0,0, {action="trigger", target="fart",
      7             interval=10})

Lines 5 to 7 demonstrate how to create individual stones.  The set_stone command takes a stone name, the desired coordinates, and an (optional) list of attributes as arguments.  Note the use of curly braces {, } to enclose the attribute list.

Attributes are the key to customizing the behaviour of objects in a landscape.  Here, we first give a name to the first stone we create. It's a fart stone that has the unpleasant habit of ``blowing off'' when triggered.  Triggering this fart stone is done by the timer stone we create in line 6--7.  This stone performs a predefined action at regular intervals.  In this case we want to send a ``trigger'' message every ten seconds to the object named ``fart''.

      9   oxyd(3,3)
     10   oxyd(level_width-4,level_height-4)
     11   oxyd(level_width-4, 3)
     12   oxyd(3,level_height-4)
     13   oxyd_shuffle()

These commands place a couple of oxyd stones in the level.  The oxyd command internally uses set_stone("st-oxyd", x,y, ...)  to create the stones, but it additionally assigns sensible values to some of the oxyd stones' attributes (most notably the color).  The command on line 14 permutes the colors on the oxyd stones currently in the landscape.

     15   set_actor("ac-blackball", 10,6.5)

This final line creates the black marble controlled by the player. Objects that can move around freely are called ``actors'' in Enigma. Unlike stones and items, actors are not restricted to integer coordinates, as you can see in this example.

Registering Levels
==================

After writing the level description you have to tell Enigma where to find your brand new landscape.  That's really two separate steps:

 1. Move the .lua-File where Enigma can find it;

 2. Insert a new entry into the appropriate level index.

The .lua-Files and the corresponding level index usually reside in the same directory.  For the levels that come with Enigma, for example, this is the levels directory inside.  For your own levels you can either use the same directory (currently your only choice if you use the Windows version of Enigma) or the .enigma/levels directory in your home folder (only if you use the Unix version).

A level index is a file that contains the list of landscapes that comprise a level pack in Enigma.  Here is an excerpt from index_enigma.txt, which defines the ``Enigma'' level pack:

     {file=welcome              name="Welcome"                        author="Daniel Heck"         }
     {file=martin06             name="Is It Easy?"                    author="Martin Hawlisch"     }
     {file=lasers101            name="Lasers 101"                     author="Daniel Heck"         }
     {file=level3a              name="Feel Your Way"                  author="Siegfried Fennig"    }
     {file=martin04             name="Sokoban Revival"                author="Martin Hawlisch"     }

Every line in this file describes one landscape in the level pack. The general format of these lines is

     { tag1=content1 tag2=content2 ... }

One line normally contains many different tag=content pairs.

If your content contains spaces, surround the content with quotes (e.g. name="Is It Easy?"). If you want the string to contain quotes, escape them with \ (e.g. author = "Petr \"ant\" Machata").

Here's a description of all supported tags:

file
     Defines the file name of the level (excluding the .lua extension). This entry is mandatory!

name
     Defines the full name of the level. This is the name the player will see in the level menu. You can leave this field empty if you prefer to leave your level unnamed.

author
     Defines the name of the autor. It will be displayed together with the full name at level startup.

revision
     Defines the revision number of the level (defaults to 1) When the revision number is increased, a small red ! appears in the level menu.

     If you do changes to the level that affect the way the level is solved, you should increase the revision number. If you only did cosmetic changes, you should NOT increase the revision.

     You should never decrease the revision number!

easymode
     Set this to 1 when the level supports different difficulties.

par_time
     Syntax: par_time=sec,name

     sec is the par time for the level in seconds.

     name is the player who did the par.

     If easymode is 1 then par_time_easy and/or par_time_normal have to be used instead of par_time.

When Enigma starts up it automatically tries to load an index file called index_user.txt, where you can store all your personal levels.  This file is not included in Enigma distributions, you have to create it yourself.  The levels listed in this file will show up in a new level pack called ``User Levels''.

Where to go from here
=====================

The example level from the first section of this chapter was hopefully enough to give you an impression how level descriptions look like in Enigma.  Of course, that level was extremely simple, and most interesting levels will be more complicated.  The rest of this reference manual tries to document the available game objects and how to interact with the Enigma game engine, both when preparing the level (before the game starts) and during the game.

This manual only describes the low-level interface to Enigma's game engine, which is as flexible as it is inconvenient to use by hand. Petr Machata has written a comprehensive set of helper routines that greatly simplify the creation of new levels.  You can use the package by including the line Require("levels/ant.lua") in your level descriptions.  There is extensive documentation for ant.lua in file ant_lua.txt in the documentation directory.

Before you read on, please be aware that this manual is far from complete.  We are working on it and it will be ready for the (glorious) 1.0 release.  For the moment, the available level descriptions are the best ``documentation'' available.

XML levels
**********

Enigma is slowly moving towards a more data-centric level description format.  Although the current use of small Lua scripts for this purpose makes it possible to create levels with sophisticated dynamic behavior, it is difficult to create large, complex levels by hand and even more difficult to write graphical tools that help level designers with this task.  The purpose of the XML-based levle format for Enigma is to provide an extensible basis for automated processing of Enigma levels, while retaining the full expressive power of the Lua scripting language where necessary or desirable.

The general outline of an XML-style Enigma level looks like this:

     <level width="20" height="13">
       <info>
          <!-- level information -->
       </info>
       <option ... />
       <actors>
          <!-- actor definitions -->
       </actors>
       <floors>
          <!-- floor definition -->
       </floors>
       <items>
          <!-- item definition -->
       </items>
       <stones>
          <!-- stone definition -->
       </stones>
       <rubberbands>
          <!-- rubberband definition -->
       </rubberbands>
       <signals>
          <!-- signal definition -->
       </signals>
       <lua>
          <!-- optional Lua code -->
       </lua>
     </level>

If you are unfamiliar with XML, here are a few general notes:

  * XML is a standard for representing hierarchical documents.  An XML document consists of a number of arbitrarily nested segments delimited by opening tags like <level> and closing tags </level>.

  * Tags can have arguments, as shown above for the level tag. Arguments have the form name="value"; note that the value must be enclosed in quotation marks.

  * The empty tag <option ... /> is an abbreviation for <option ...></option>.

  * Comments can be written like this <!-- blabla -->.

An Enigma level must begin with <level width="xx" height="yy">, where xx and yy are width and height of the level, and ends with </level>  The following sections of this manual describe the structure of the remaining parts of a level description, in the order indicated in the above example.

Meta information
================

Every level should begin with a short block containing general information about the level.  This can include the level name, its author and license restrictions.  If you intend your level(s) to be distributed with Enigma, the following four fields are mandatory:

     <info>
       <name>LEVEL NAME</name>
       <author>AUTHOR NAME</author>
       <copyright>COPYRIGHT NOTICE</copyright>
       <license>LICENSE TERMS</license>
     </info>

Level options
=============

Certain aspects of the game can be customized by changing the values of the options to be described in this section.  Some of these options control general aspects, like constant force fields or whether the level automatically restarts when the marble gets destroyed, while other options provide default values for objects in the level, like the strength of magnetic fields or the look of Oxyd stones.

The following example shows the general syntax for options.  Note the use of empty tags: the salient information is already contained in the attributes NAME and VALUE.  Boolean options are always encoded as ``YES'' or ``NO''.

     <option name="shuffle" value="NO" />

Here is the table of all options available so far:

shuffle
     Shuffle the colors of the Oxyd stones after before starting the game? "YES"/"NO".

oxydflavor
     The look of Oxyd stones; "a"/"b"/"c"/"d". See st-oxyd for details.

reset
     Reset the level when the player dies? "YES"/"NO"

scrolling
     An integer between 1 and 4 (inclusive).  Determines how the screen follows the currently active ball. 1: scroll the screen, 2: flip the screen, 3: scroll but align to screens, 4: keep marble at center.

In addition, there are a few numeric options that determine the behavior of certain comon objects.  These correspond to the variables desribed later in the document, see Variables for details.

brittleness

slopeforce

flatforce

frictionfactor

electricforce

bumperforce

magnetforce

magnetrange

wormholeforce

wormholerange

holeforce

Actors
======

Syntax:

     <actors>
       <actor kind=äc-blackball x=10.5 y=5.5 />
     </actors>

     <actors difficulty=ḧard>
       <actor kind=äc-killerball" x=3 y=4 attribs=c̈ontrollers=3 />
     </actors>

     <actors difficulty=ëasy>
       <actor kind=äc-killerball" x=3 y=4 attribs=c̈ontrollers=0 />
     </actors>

Objects
=======

The description of floor tiles, items, and stones in the XML level file is very similar, so we treat them here in one section.  The general syntax looks like this:

     <floors>
       <row y=ÿy> ... </row>
       <floor kind=n̈ame x=ẍx y=ÿy attribs=ättriblist />
     </floor>

For items and stones, the XML tags are called <items> and <stones> respectively.  As for the actor sections, you can optionally include a difficulty= option to place certain objects only in the specified difficulty level.

The <row> tag can be used to draw complete rows of objects to the screen.  An example looks like this:

     <floors>
       <row y=10>abyss 10 water # abyss 10 </row>
     </floors>

This must be read as follows: In the tenth row, put one fl-abyss (not that the prefix is not included in the level file!), repeat it ten more times (so it's elevel abyss tiles), put one water tile, repeat it once, and then finish with another eleven abysses.

Here's another, more advanced, example for a row of items:

     <items>
       <row y=10>-10 hammer - - blackbomb - # -5 3</row>
     </items>

Read this as follows: skip 10 fields, put one hammer, skip two fields (you could also write -2 instead), put one black bomb, skip one field, put another black bomb, skip five fields, and finish with three more black bombs.

In general there can be five different kinds of entries in such a row description, all of them separated by spaces:

name
     Put one object of the specified type at the current position, remember the object name;

#
     Repeat the last named object

positive number
     Repeat the last named object the specified number of times

-
     Skip one field

negative number
     Skip the specified number of fields

You cannot specify object attributes using <row> tags, to do this you must place objects individually, using either <floor ... />, <item ... />, or <stone ... />, for example

     <stones>
       ...
       <stone kind=s̈t-switch x=2 y=2 attribs=äction='openclose', target='door1' />
       ...
     </stones>

The attribute list looks like the one in Lua would, except for the enclosing braces {} that must be omitted in the XML level format.  Please note that you must in this case use single quotes ' to enclose string attributes, double quotes would terminate the XML argument.  Enigma's current XML parser unfortunately does not yet understand character entities like &quot;, this will hopefully be fixed in future versions.

Signals
=======

[To be written]

Rubberbands
===========

Syntax:

     <rubberbands>
       <rubberband from=öbjname to=öbjname strength=12 length=5 minlen=0 />
     </rubberbands>

Embedded Lua code
=================

To make XML levels every bit as expressive as the former level format, a special <lua> tag is available to carry arbitrary Lua code. Only one such tag per level is allowed, and the code it contains is executed after all other tags have been processed, immediately before handing the level over to the game engine.

Lua code blocks can be used for everything that can not be realized with the data-centric XML format, like specially crafted signal handlers, randomly generated levels or puzzles, or to access features of Enigma's game engine that are not otherwise available.

Graphical level editors are expected not to tamper with the contents of Lua code blocks when they read or write Enigma levels, i.e., neither to modify them nor to delete them without notice.

Objects
*******

Floors
======

Special floor tiles
-------------------

     fl-abyss
     fl-acblack
     fl-acwhite
     fl-bridge( type )
     fl-bridge-closed( type )
     fl-bridge-open( type )
     fl-gradient( type )
     fl-gradient{1..16}
     fl-springboard
     fl-swamp
     fl-water

Regular floor tiles
-------------------

     fl-abyss_fake
     fl-black
     fl-bluegray
     fl-bluegreen
     fl-bluegreenx
     fl-brick
     fl-bumps
     fl-concrete
     fl-darkgray
     fl-dummy
     fl-dunes
     fl-floor_001
     fl-gravel
     fl-gray
     fl-hay
     fl-himalaya
     fl-ice
     fl-ice_001
     fl-inverse
     fl-inverse2
     fl-leaves
     fl-leavesb
     fl-leavesc{1..4}
     fl-leavesd{1..4}
     fl-leavese{1..4}
     fl-light
     fl-lightgray
     fl-marble
     fl-metal
     fl-metal{1..6}
     fl-mortar
     fl-normal
     fl-normal_x
     fl-plank
     fl-red
     fl-rock
     fl-rough
     fl-rough-blue
     fl-rough-red
     fl-rough_medium
     fl-rough_slow
     fl-sahara
     fl-samba
     fl-samba1
     fl-samba2
     fl-sand
     fl-space
     fl-space-force
     fl-stone
     fl-stwood
     fl-stwood1
     fl-stwood2
     fl-tigris
     fl-trigger
     fl-white
     fl-wood
     fl-woven

Items
=====

Item List
---------

     it-1pkillstone
     it-2pkillstone
     it-abyss
     it-bag
     it-banana
     it-blackbomb
     it-blackbomb_burning
     it-blocker
     it-blocker-new
     it-booze
     it-brake
     it-bridge-oxyd
     it-bridge-oxyd_active
     it-brush
     it-burnable
     it-burnable_ash
     it-burnable_burning
     it-burnable_fireproof
     it-burnable_ignited
     it-changefloor
     it-cherry
     it-coffee
     it-coin1( value )
     it-coin2( value )
     it-coin4( value )
     it-crack{0..3} ( type fixed brittleness )
     it-cross
     it-debris
     it-document( text )
     it-drop
     it-dummy
     it-dynamite
     it-easykeepstone
     it-easykillstone
     it-explosion1
     it-explosion2
     it-explosion3
     it-extinguisher( load )
     it-extinguisher_empty( load )
     it-extinguisher_medium( load )
     it-extralife
     it-flagblack
     it-flagwhite
     it-floppy
     it-glasses
     it-glasses-broken
     it-hammer
     it-hill
     it-hollow
     it-hstrip
     it-inversesensor
     it-key( keycode )
     it-key_a
     it-key_b
     it-key_c
     it-landmine
     it-magicwand
     it-magnet( on strength range )
     it-magnet-off( on strength range )
     it-magnet-on( on strength range )
     it-odometer
     it-oxyd5f
     it-pencil
     it-pin
     it-pipe-e
     it-pipe-es
     it-pipe-h
     it-pipe-n
     it-pipe-ne
     it-pipe-s
     it-pipe-sw
     it-pipe-v
     it-pipe-w
     it-pipe-wn
     it-puller-e
     it-puller-n
     it-puller-s
     it-puller-w
     it-ring
     it-rubberband( object1 object2 length strength )
     it-seed
     it-seed_nowood
     it-seed_volcano
     it-sensor
     it-shogun-l
     it-shogun-m
     it-shogun-s
     it-signalfilter0
     it-signalfilter1
     it-spade
     it-spoon
     it-spring1
     it-spring2
     it-springboard
     it-squashed
     it-surprise
     it-sword
     it-tinyhill
     it-tinyhollow
     it-trigger( invisible )
     it-umbrella
     it-vortex-closed( autoclose targetx targety )
     it-vortex-open( autoclose targetx targety )
     it-vstrip
     it-weight
     it-whitebomb
     it-wormhole( on targetx targety strength range )
     it-wormhole-off( on targetx targety strength range )
     it-wrench
     it-yinyang

it-document: Scrolls of Paper
-----------------------------

This item looks like a piece of paper and contains text messages that can be displayed by activating the item.

Attributes

text
     The message to be displayed.

Example

     set_item("it-document", 1,1, {text="Hello World!"})
     Document(1,1, "Hello World")

it-floppy: Floppy Disk
----------------------

The floppy disk is needed to activate the Floppy switch (see st-floppy).

it-hollow: Hollows in the floor
-------------------------------

This item creates a hollow in the floor. If all existing ac-whiteball-small are inside hollows the level succeeds.

Attributes

essential
     Whether the hollow must be filled with a whiteball to end the level (1 means 'yes').

     Use this attribute if there are more holes than small whiteballs in a level and you want to determine which of the holes are needed to finish the level.

     For example: If you have many holes and 3 whiteballs, then set essential=1 in 3 holes.  The game will end when the 3 whiteballs are inside the 3 marked holes.

it-ring: Ring
-------------

When a player drops this item, the marble is teleported.  The destination depends on the game mode:

Single player levels:
     The marble is transported to its starting position or to the position of the last dropped it-flag.

Multi player levels:
     Both marbles exchange their positions.

it-vortex: Vortex
-----------------

Vortices, like wormholes, can be used to teleport marbles.  In the simplest case, every vortex is connected to exactly one other vortex. If there are multiple target vortices, the marble will be teleported to the first unblocked target site.  Many levels in the original Oxyd games required the player to selectively block vortices to gain access to new parts of the level.

Example

This example creates three vortices.  If the second vortex is blocked, a marble falling into the first one is transported to (20,1).

     set_item ("it-vortex", 1, 1)
     set_item ("it-vortex", 10,1)
     set_item ("it-vortex", 20,1)
     Signal ("it(1 1)", "it(10 1)")
     Signal ("it(1 1)", "it(20 1)")
     Signal ("it(10 1)", "it(1 1)")
     Signal ("it(20 1)", "it(1 1)")

Stones
======

Stone List
----------

Simple stones

The following stone types are commonly used for ``decoration''.  They generally do not have special properties or abilities.  Three types of abbreviations are used in the tables: [abc] stands for any of the characters in square brackets, <abc> stands for any subsequence of the characters between the angle brackets (in this case abc, ab, bc, a, b, c), and {1..9} indicates a sequence of numbers.

     st-beads
     st-bigbrick-<nesw>
     st-blue-sand
     st-bluegray
     st-bluegray_hole
     st-brick
     st-brownie
     st-bumps
     st-dummy
     st-fakeoxyd( blinking )
     st-fakeoxyda
     st-glass
     st-glass[123]
     st-glass[12]_hole
     st-glass1_move
     st-glass_move
     st-grate{1..3}
     st-greenbrown
     st-greenbrown_hole
     st-greenbrown_move
     st-likeoxyd[abcd]
     st-likeoxyd[abcd]-open
     st-marble
     st-marble_hole
     st-marble_move
     st-metal
     st-plain
     st-plain_hole
     st-plain_move
     st-rock{1..8}
     st-rock[123]_hole
     st-rock[13]_move
     st-stone[12]
     st-wood[12]
     st-wood_001
     st-woven
     st-yellow

Special stones

The following stones types are special in the sense that they perform some action, either when hit by an actor, or all by themselves.

     st-3mirror( transparent movable orientation )
     st-actorimpulse
     st-actorimpulse_invisible
     st-black{1..4}
     st-blackballs
     st-block
     st-blocker
     st-blocker-growing
     st-bolder-[ensw]
     st-bombs
     st-brake
     st-break_acblack
     st-break_acwhite
     st-break_bolder
     st-break_gray
     st-break_invisible
     st-breaking
     st-brick_magic
     st-bug
     st-chameleon
     st-chargeminus( charge )
     st-chargeplus( charge )
     st-chargezero( charge )
     st-coffee
     st-coinslot( on )
     st-death
     st-death_invisible
     st-disco-dark
     st-disco-light
     st-disco-medium
     st-door( type )
     st-door-h( type )
     st-door-h-open( type )
     st-door-v( type )
     st-door-v-open( type )
     st-door_[abc]
     st-easymode
     st-explosion
     st-fart
     st-flash
     st-floppy( on )
     st-fourswitch( on )
     st-greenbrown-growing
     st-invisible
     st-invisible_magic
     st-key( on keycode )
     st-key_[abc] ( on keycode )
     st-knight
     st-laser-[ensw]( on )
     st-laserbreak
     st-laserswitch
     st-lasertimeswitch( delay )
     st-magic
     st-mail-[ensw]
     st-mirror-3<
     st-mirror-3<m
     st-mirror-3<t
     st-mirror-3<tm
     st-mirror-3>
     st-mirror-3>m
     st-mirror-3>t
     st-mirror-3>tm
     st-mirror-3^
     st-mirror-3^m
     st-mirror-3^t
     st-mirror-3^tm
     st-mirror-3v
     st-mirror-3vm
     st-mirror-3vt
     st-mirror-3vtm
     st-mirror-p-
     st-mirror-p-m
     st-mirror-p-t
     st-mirror-p-tm
     st-mirror-p/
     st-mirror-p/m
     st-mirror-p/t
     st-mirror-p/tm
     st-mirror-p\
     st-mirror-p\m
     st-mirror-p\t
     st-mirror-p\tm
     st-mirror-p|
     st-mirror-p|m
     st-mirror-p|t
     st-mirror-p|tm
     st-oneway-[nesw]
     st-oneway_black-[nesw]
     st-oneway_white-[nesw]
     st-oxyd( flavor color )
     st-oxyd-0x18
     st-peroxyd-0xb8
     st-peroxyd-0xb9
     st-plain_break
     st-plain_breaking
     st-plain_cracked
     st-plain_falling
     st-pmirror( transparent movable orientation )
     st-pull
     st-puzzle-hollow( oxyd )
     st-puzzle-<nesw>( oxyd )
     st-puzzle2-hollow( oxyd )
     st-puzzle2-<nesw>( oxyd )
     st-rock3_break
     st-rock3_movebreak
     st-rotator-left
     st-rotator-right
     st-rotator_move-left
     st-rotator_move-right
     st-rubberband( length strength )
     st-scissors
     st-shogun-<sml>
     st-spitter
     st-stone_break
     st-stonebrush
     st-stoneimpulse
     st-stoneimpulse-hollow
     st-stoneimpulse_movable
     st-surprise
     st-swap
     st-switch( on )
     st-switch_black( on )
     st-switch_white( on )
     st-thief
     st-timer( on interval loop invisible )
     st-timeswitch( delay )
     st-turnstile
     st-turnstile-green
     st-turnstile-[ensw]
     st-volcano
     st-volcano-growing
     st-volcano_active
     st-volcano_inactive
     st-white{1..4}
     st-whiteballs
     st-window
     st-wood
     st-wood-growing
     st-yinyang{1..3}

st-actorimpulse: Bumper Stones
------------------------------

These stones apply an impulse to actors that touch them.  The amount of force applied can be controlled by setting enigma.BumperForce accordingly (the default is 800). Alternatively, the force attribute can be used to set this factor for individual bumper stones.

The invisible variant, st-actorimpulse_invisible can ``painted'' with a it-brush.

st-chameleon: Chameleon Stone
-----------------------------

This stone takes on the look of the floor beneath it.  Actors can move through it, so these stones are perfect for hiding stuff under them...

st-coinslot
-----------

A switch that can be activated with coins.  The more coins you put in, the longer the switch will stay activated.

Attributes

target, action
     As usual

st-death: Skull Stones
----------------------

Simply kills all marbles that touch it (except when protected by an umbrella).

Variants

st-death

st-death_invisible

st-disco: Disco Stones
----------------------

Darkens everything that is underneath the stone (much like tinted glass).  Can be switched on and off (hence the name).

Messages

signal
     With parameter 1, lighten the stone and (recursively) all neighboring disco stones; with parameter smaller than 1, darken them.

lighten

darken

Variants

st-disco-light

st-disco-medium

st-disco-dark

st-easymode: Easy Mode Stone
----------------------------

In easy game mode this stone converts the floor at its position to fl-normal.  In normal game mode the stone removes any item at its position.  The stone itself never appears in either game mode; it removes itself immediately after performing its job.

This stone is commonly used to hide danger areas (water holes, abyss) or to insert helper items (umbrellas, seeds, etc.) that make the level easier in easy game mode.

st-fart: Fart Stone
-------------------

The fart stone has the unpleasant habit of ``blowing off'' when triggered (by actor hit or signal) and will close all Oxyd stones.

Messages

trigger
     blow off

st-floppy: Floppy Switch
------------------------

A switch that is activated by inserting a floppy disk (see it-floppy).

Attributes

on
     1 or 0

target

action

st-grate: Grates
----------------

Floating grates, mainly decorative.  Flying objects (jumping marbles, rotors, etc.) cannot pass, objects moving on the floor can.

Variants

st-grate1

st-grate2

st-grate3

st-laserswitch: Laser Switch
----------------------------

This switch is on while hit by a laserbeam and off when not hit by a laserbeam.

See also st-lasertimeswitch.

Attributes

inverse=1
     Inverts the on/off state of the switch (i.e on at startup and switch off with laserbeam)

target,action
     as usual

st-lasertimeswitch: Laser Time Switch
-------------------------------------

This switch is a mix between st-laserswitch and st-timeswitch.

st-oneway: One-way Stones
-------------------------

This stone can be passed by the marble in only one direction. (Or, to be more exact, the arrow on the stone points to the one side of the stone through which it can't be entered.  Hard to explain, try it yourself :-)

There are three different variants of the one-way stone: the standard one, st-oneway, which both the black and the white marble can pass, and two colored ones, st-oneway_black and st-oneway_white, which completely block marbles of the other color.

Variants

st-oneway

st-oneway-[nesw]

st-oneway_black

st-oneway_black-[nesw]

st-oneway_white

st-oneway_white-[nesw]

Attributes

orientation
     One of NORTH, EAST, SOUTH, or WEST.  This determines the orientation of the stone when the level is loaded.  You need to use the direction message for changing the orientation during the game.  Note that it is usually easier to use one of the alternative names, like st-oneway-north instead of explicitly setting this attribute.

Messages

direction
     Set the direction of the arrow during the game.  Simply setting the attribute orientation is not enough, since this does not update the stone's model on the screen.

signal

flip
     Both these messages flip the direction of the arrow.

st-oxyd: Oxyd Stones
--------------------

Oxyd stones are characterized by two attributes: Their flavor and their color.  The flavor only affects the visual representation of the stone; it can be either `a' (opening like a flower), `b' (displaying a fade-in animation), `c', or `d'.  The color attribute determines the color on the oxyd stone.

Note: You should rarely need to create Oxyd stones manually with set_stone().  Use the predefined oxyd() function instead.  It will automatically take care of creating two Oxyd stones of every color.

Attributes

flavor
     `a', `b', `c', or `d'

color
     a number between 0 and 7

Messages

closeall
     Close all oxyd stones

shuffle
     Interchange the colors of the oxyd stones in the current landscape. Use the oxyd_shuffle() function.

trigger
     Open the stone (useful for opening Oxyd stones using switches)

st-rubberband: Rubberband Stone
-------------------------------

If hit by a marble, this stone first removes existing connections with other rubberband stones and then attaches a new elastic between the marble and itself.  Nothing happens if the marble was already attached to this particular stone.

This stone can be moved if hit with a magic wand.

Attributes

length
     The natural length of the rubberband (default: 1)

strength
     The strength of the rubberband (default: 10)

st-scissors: Scissors Stone
---------------------------

This stone cuts all rubber bands attached to an actor that touches it.

st-stone_break: Breakable Stone
-------------------------------

This stone can be destroyed by an actor having a hammer and by laser, dynamite, bombs and bombstones.

st-swap: Swap Stone
-------------------

This stone can exchange its position with other neighboring stones if it is hit hard enough.  In a way, this makes swap stones a kind of "movable stone", except that they can be only exchanged with other stones and may not be moved on empty fields.

st-switch: Switches
-------------------

A simple switch.

Variants

st-switch
     All kinds of objects can activate this switch

st-switch_black
     Only black marbles can activate this switch

st-switch_white
     Only white marbles can activate this switch

Attributes

on
     1 (activate) or 0 (inactive)

target, action
     as usual

st-thief: Thief Stone
---------------------

Takes one item from inventory after when hit by the player's marble. Umbrellas protect against thievery.

st-timer: Timer Stone
---------------------

This stone can be used to trigger periodic events or to trigger one single event after a certain amount of time.

Attributes

on
     1 if the timer is running

interval
     number of seconds before action is performed

loop
     if 1, restart the timer after performing action

action
     as usual

target
     as usual

invisible
     if 1, stone is invisible

Messages

on

off

onoff

Example

     -- activate a laser after 5 seconds
     set_stone("st-laser", 10,11, {name="laser"})
     set_stone("st-timer", 10,10,
               {loop=0, action="onoff", target="laser", interval=5})

st-timeswitch: Time Switch
--------------------------

When this switch is touched by an actor, it switches on for 1.8 seconds and then switches off again.

See also st-lasertimeswitch.

Attributes

delay
     The delay in seconds after which the switch goes off.

inverse=1
     Inverts the on/off state of the switch.

st-window: Breakable Stone
--------------------------

Hit this window heavily with your marble to blast it into smithereens.

st-wood: Wooden Stone
---------------------

This stone is movable.  If moved into abyss, water or swamp it builds a wooden plank.

Note: There are two flavors of st-wood which may be specified by using st-wood1 or st-wood2.

st-yinyang: Yin-Yang Stones
---------------------------

Yin-Yang stones change into st-white or st-black if you touch them.

There are several flavors of this stone:

st-yinyang1
     If touched it changes it's color to the opposite color of your marble.

st-yinyang2
     If touched it changes it's color to the same color as your marble.

st-yinyang3
     The Per.Oxyd compatible: You must hold it-magicwand or it-brush to change the color to the opposite color of your marble.

Actors get stuck inside the Yin-Yang Stone if they are starting there or when they warp there. They can be freed by changing the color of the Yin-Yang Stone to their color.

Actors
======

Movable objects are called ``actors'' in Enigma.  The commonest actor is, of course, the black marble, but there are others, including the white marble, the killerball and a few more:

ac-blackball
------------

mouseforce (default 1.0) color (default 0.0) blackball (default 1) player (default 0) controllers (default 1)

ac-whiteball
------------

mouseforce (default 1.0) color (default 1.0) whiteball (default 1) player (default 1) controllers (default 2)

ac-whiteball_small
------------------

mouseforce (default 1.0) color (default 1.0) whiteball (default 1) controllers (default 3)

ac-killerball
-------------

mouseforce (default 2.0) color (default 1.0) whiteball (default 1) controllers (default 3)

ac-rotor
--------

range (default 5.0) force (default 10.0) gohome (default 1)

ac-top
------

range (default 5.0) force (default 10.0) gohome (default 1)

ac-bug
------

ac-horse
--------

force (default 10.0) target1 target2 target3 target4

Actor Attributes
----------------

All actors share a set of common attributes that determine their general behaviour:

player
     The player ``owning'' this actor.  This is either 0 or 1 for the first or second player respectively.  Actors attached to a player can pick up items and can be respawned when they are killed.

mouseforce
     A factor that determines how much the actor accelerates when the mouse is moved.  Default is 1, use higher values for fast moving actors.  If set to 0, the actor cannot be moved with the mouse (but external forces can still exert a force on it).

controllers
     Determines which players may move this actor: 1=Player 1, 2=Player 2, 3=both. By default, ac-blackball, ac-whiteball and ac-whiteball-small have their controllers attribute set to 1,2, and 3 respectively.

essential
     A non-zero value marks this actor as essential.  If essential=1, the game restarts if 1 of all essential actors can't resurrect (analog for higher values).  If you set the attribute for several actors, you should use the same value for all of them!

whiteball, blackball
     Used by color-sensitive stones (black/white switches for example) to determine whether the actor is the black or the white marble.  These attributes may disappear in future versions, please do not use them.

General object attributes
=========================

name
     All objects may be given a name attribute. Such named objects can be searched using enigma.GetNamedObject.

Variables
*********

This chapter describes the a few variables that can be changed from level descriptions to alter the behavior of the game engine or set default attributes for some particular objects.  In the latter case, the same effect can usually be achieved by setting the corresponding object attributes directly, but being able to specify a global default value it is often more convenient.  You can always override these default attribute values for specific objects by setting the appropriate object attributes.

 -- Variable: enigma.ConserveLevel
     TRUE or FALSE.  If FALSE, reload the level whenever the an actor that is controlled by a player (i.e., one that has the player attribute set) dies.  Often used in meditation landscapes or landscapes that are intended to be solved in one go. Default: TRUE.

 -- Variable: enigma.ShowMoves
     TRUE or FALSE.  This is only used in the Sokoban level pack to display a move counter in the inventory. Default: FALSE.

 -- Variable: enigma.Brittleness
     A value between 0 and 1, denoting the probability that a brittle floor plate desintegrates further when an actor enters or leaves it.  1 means that the floor will always crack, 0 that it is indestructible. Default: 0.5.

 -- Variable: enigma.BumperForce
     The amount of force applied to an actor that hits an st-actorimpulse stone.  st-actorimpulse. Default: 200.0.

 -- Variable: enigma.ElectricForce
     A force multiplier for all electric forces between actors. Default: 15.0.

 -- Variable: enigma.FrictionFactor
     All friction forces are multiplied by this value. Default: 1.0.

 -- Variable: enigma.FlatForce
     A global downward force.  This is currently only applied on floors of type fl-space.  Default: 0.

 -- Variable: enigma.HoleForce
     A force factor that affects the steepness of hollows and hills. Default: 1.0.

 -- Variable: enigma.MagnetForce
     A force multiplier for magnetic fields.  Default: 30.0.

 -- Variable: enigma.MagnetRange
     The range of magnetic fields.  Default: 10.0.

 -- Variable: enigma.SlopeForce
     A force multiplier for sloped floor tiles.  Default: 25.0.

 -- Variable: enigma.WaterSinkSpeed
     How quickly balls sink in water.  Default: 1000.0.

 -- Variable: enigma.SwampSinkSpeed
     How quickly balls sink in swamp.  Default: 4.0.

 -- Variable: enigma.WormholeForce
     A force multiplier for wormholes.  Default: 30.0.

 -- Variable: enigma.WormholeRange
     The range of worm holes.  Default: 10.0.

Functions
*********

AddRubberBand
=============

 -- Function: AddRubberBand (actor, object, strength, length)

     This function connects two objects with a rubber band: The first object is always an actor, the second object can be either another actor or a stone.

     The first argument ACTOR is always a reference to an actor created earlier with the set_actor function.  The second parameter OBJECT may be either an actor or a stone created earlier.  The last two parameters define the properties of the rubber band: STRENGTH denotes the force factor of the elastic and LENGTH its natural length.  No force is exerted on the actor if the rubber band is shorter than its natural length.

Example
-------

     local ac=set_actor("ac-blackball", 1.5,7.5)
     local st=set_stone("st-brownie", 10,6)
     AddRubberBand(ac, st, 50, 10)

CreateWorld
===========

 -- Function: CreateWorld (width, heigth)

     This function creates a new level. Because objects can only be added to the level after CreateWorld has been called, you should usually do so near the beginning of your level description.

     The WIDTH and HEIGHT denote the size of the new level.  All levels with only one screen have the minimum size of 20x13 blocks.

     Note that level fields are indexed from zero, i.e, the field indices for a 20x13 level are in the range (0..19)x(0..12). Also note that the screens in Enigma overlap by one line or column: A level that fits on a single screen has size of 20x13, but two a level that is two screens wide 39x13 or 20x25, three screens 58x13 or 20x37.

enigma.AddConstantForce
=======================

 -- Function: enigma.AddConstantForce (gravity_x, gravity_y)

     Adds global gravity to the current level.

     gravity_x
          adds gravity in horizontal direction (positive means rightwards).

     gravity_y
          adds gravity in vertical direction (positive means downwards).

enigma.GetNamedObject
=====================

 -- Function: enigma.GetNamedObject (objname)

     This function searches for an object that has a name attribute with value OBJNAME.  It returns a reference to the object or nil if none could be found.

Example
-------

     set_stone("st-wood", 7, 11, {name="woodie"})
     ...
     local Woodie = enigma.GetNamedObject("woodie")

SendMessage
===========

 -- Function: SendMessage (object, message, data)

     This function sends a MESSAGE to an OBJECT.

     object
          The recipient of the message.  Can either be the name of an object or a reference as returned by enigma.GetNamedObject.

     message
          The message itself (e.g. "signal") You can see which messages are understood in the documentation of the particular Objects.

     data
          Some specific messages expect some additional data (e.g. message "direction" expects a direction like SOUTH or WEST).

Examples
--------

     set_stone("st-laser-s", 2, 2, {name="laser3", on=FALSE})
     ...
     SendMessage("laser3", "onoff")

     set_stone("st-bolder", 7, 11, {name="bolder1", direction=SOUTH})
     ...
     SendMessage("bolder1", "direction", WEST)

draw_checkerboard_floor
=======================

 -- Function: draw_checkerboard_floor (name1, name2, x, y, w, h, attribs)

     This function draws checkerboard composed of two selected floor types. NAME1 and NAME2 are names of floor objects. See set_floor for further details.

     name1, name2
          Names of floor objects

     x, y
          Location of left top corner of checkerboard area. Note that upper left map corner is [0,0].

     w, h
          Size of generated checkerboard.

     attribs
          Table of attribute names and corresponding values: {attrib1=value1, attrib2=value2, ...}. These attributes, together with default attributes, are passed to each tile of the generated checkerboard.

Example
-------

     draw_checkerboard_floor("fl-abyss", "fl-rough", 2, 2, 23, 11)
     draw_checkerboard_floor("fl-normal", "fl-inverse", 0, 0, levelw, levelh) -- racetrack

draw_border
===========

 -- Function: draw_border (stonename, x,y, w,h)

     This function adds a border of stones to your level.  If invoked with only one argument, this border encloses the whole level.

     stonename
          The name of the border stone.

     x,y
          (optional) Coordinates of upper-left corner. (0,0) if omitted.

     w,h
          (optional) Width and height of border.

Example
-------

     draw_border("st-marble")
     draw_border("st-greenbrown", 0,5,3,3)