This document discusses domain-specific languages (DSLs) for games. It begins by defining DSLs and distinguishing them from scripting languages. An example DSL called Tracery is presented for generating text. Another DSL called Ephemerald is shown, which is similar to Tracery but integrated into a browser. Additional examples of game DSLs are provided, like the Game Maker Language (GML) and PuzzleScript for puzzle games. Historical examples of game DSLs are also outlined. The talk concludes by discussing considerations for creating your own DSL.

1. Shibboleth Scripting
DOMAIN-SPECIFIC LANGUAGES FOR GAMES
MARTIN PICHLMAIR
IT UNIVERSITY COPENHAGEN / BROKEN RULES / COPENHAGEN GAME COLLECTIVE

2. SHIBBOLETH?

4. PLEASE RAISE YOUR HAND IF
YOU CAN PROGRAM!

5. PLEASE RAISE YOUR HAND IF
YOU CAN WRITE!

6. WHO HERE HAS EVER
WRITTEN A GRAMMAR?

7. AND WHO HAS
INVENTED A LANGUAGE?

8. DOMAIN SPECIFIC LANGUAGES
Markup Languages
Modelling Languages
Programming Languages

9. DOMAIN SPECIFIC LANGUAGES
Human-readable
Computer-readable
Made for a specific domain, not general purpose

10. DOMAIN SPECIFIC LANGUAGES
Difference to “scripting language”:
a) Actually a DSL can be a scripting language. A scripting language
can be domain-specific after all, think GameMaker Language.
b) Whether a DSL is more suited for you than a generic scripting
language depends on many factors.

11. LET’S LOOK AT AN EXAMPLE

12. TRACERY

14. Tracery
Code
Text
SVG
HTML
Tracery
Browser

17. DSL
Code
Lexer Parser Result
Grammar Code

18. EPHEMERALD

19. Ephemerald download (free): https://martinpi.itch.io/ephemerald

20. Tracery
Code
Text
SVG
HTML
Ephemerald
Browser
GML
+ A nice interface with syntax highlighting and autocomplete
+ Deterministic random (seeds)
+ Probabilities
+ Shuffle bag instead of pure random for rule selection
+ Math functions
+ Regular Expressions

21. MY BOT ARMY

22. Cooking
Recipe
Ingredients Dish

23. HOUSEHOLD CONSTELLATIONS

24. LIVE DEMO TIME

25. NARRATIVE TOOLS

29. ink code
Dynamic
Dialogs
ink
Game

30. WHAT I WON’T TALK ABOUT
I will not talk about them, though one could argue that they are DSLs:
– Scratch, Logo and the likes
– Erlang, Prolog and friends
– TinyMUD, LPMud, DikuMUD, and other MUD code bases
– Code Red, TIS-100 and other in-game languages
Why? I only have 45 minutes …

31. THE DIKUMUD FAMILY TREE

32. GAME CREATION TOOLS

33. Ludii (Maastricht University, 2019)
https://www.ludii.games

34. Fighter Maker
OUTBACK/Kuusou Kagaku 1998
RPG Maker
ASCII/Enterbrain 1992
Ren’Py
Tom "PyTom" Rothamel 2004

35. HISTORICAL EXAMPLES
Game Adaptation Language and Sierra Creative Interpreter
ZIL, Inform and Inform 6 all compile to “Z-Machine code”, Infocom
SCUMM, Lucasfilm Games
Adventure Game Studio has a domain-specific scripting language

36. INFORM 6

37. SCUMM

38. LUA DOESN’T COUNT :P

39. PUZZLESCRIPT

40. Graphics
Map Symbols
Collisions
Gameplay
Levels

41. [ > Player | Crate ] -> [ > Player | > Crate ] [ < Player | Crate ] -> [ < Player | < Crate ]

42. PuzzleScript
code
Levels
Graphics &
Sound
Rules

45. PuzzleScript
code
Levels
Graphics &
Sound
Rules
Game
Engine

46. DESCRIBING VIDEO GAMES

47. VGDL

49. BasicGame
SpriteSet
moving > physicstype=GravityPhysics
avatar > PlatformerAvatar img=newset/man1 jump_strength=5
wall > Immutable img=oryx/wall1
goal > Immovable img=newset/flag1
ladder > Ladder img=newset/ladder2
TerminationSet
SpriteCounter stype=goal win=True scoreChange=100
SpriteCounter stype=avatar win=False scoreChange=-100
InteractionSet
avatar EOS > killSprite
goal avatar > killSprite
moving wall > wallStop
avatar ladder > onLadder
LevelMapping
G > goal
★ > goal
w > wall
A > avatar
H > ladder

50. VGDL FEATURES
• Spawning, cloning and elimination of
objects, as well as transformation from one
type into another.
• Self-propelled movements of objects, taking
consistent or random actions, or erratically
changing direction.
• Non-deterministic chasing and fleeing
behaviors.
• Projectile objects, spawned at the location of
arbitrary objects, on fixed or random
schedules, based on user actions, or
triggered by collision effects.
• Stickiness, i.e., one object pulling another
one.
• Bouncing and wrap-around behavior, from
other objects or the edge of the screen.
• Teleportation of objects, to fixed or random
end- locations.
• Continuous physics effects like inertia,
friction and gravity.
• Stochastic effects like slipping in the current
direction, or wind gusts.

51. VGDL code Levels
(Graphics)
Rules

52. VGDL

53. Mads Johansen
@pyjamads

54. Unity
VGDL code Levels
(Graphics)
Rules

55. BRAIN TRAINING

57. ML-AGENTS

59. VGDL code Levels
(Graphics)
Rules
Agents

61. Unity
VGDL code
Levels
Scene
Graph
Gameplay
Sprites

62. GAMES BY ANGELINA

63. DECKART

64. Deckart
code
Rules
Card Texts

65. Deckart
Code
Coco/R
Deckart
Runtime
Card Game
Deckart
Language
Swift
Code

66. Schnapsen
(Anonymous genius, <1715)
Ascension
(Stone Blade Entertainment, 2011)

68. THE FINAL FORM

69. Deckart
code
Coco/R
Deckart
Runtime
Card Game
Deckart
Language
Swift
C#
Deckart
Runtime
Card Game

70. Deckart
code
Rules
Tracery
Code
Card Texts
Ephemerald
Deckart
Card
Layouts

71. The Design Space of
All Kinds of
Potential
Card Games
Generate
Generate
Generate
Generate

72. SO YOU WANT TO WRITE
YOUR OWN DSL?

73. DSL
Code
Lexer
Parser
Generator
Grammar Code
ResultParser

74. Lexer Parser Parser Combinators
C#* Garden Points Lexer
Hime
Grammatica
GPPG
Sprache
Superpower
Parseq
Swift
OysterKIT
Coco/R
FootlessParser
SwiftParsec
C/C++ lex yacc/bison pcomb
Java ANTLR jparsec
*Here is a good article: https://tomassetti.me/parsing-in-csharp

75. Grammar Outline
(word processor)
Grammar in EBNF
(text editor)
Lexing & Parsing
(command line)

76. Grammar Outline
(word processor)
Grammar in EBNF
(text editor)
Lexing & Parsing
(command line)
Experimental Code in DSL
(text editor)

77. Grammar Outline
(word processor)
Grammar in EBNF
(text editor)
Lexing & Parsing
(command line)
Experimental Code in your DSL
(text editor)
Native Code
(IDE of choice)

78. THANKS TO
Everyone who was involved in any of the projects I’ve talked about
today. Especially @pyjamads for UnityVGDL implementation.
Special thanks to @zarawesome, @alphachar, @aeonofdiscord,
@pyjamads, @mtrc, @EigenLenk, @PetriPurho, and others for
feedback on Twitter.

79. QUESTIONS?
Martin Pichlmair
@martinpi
mpic@itu.dk
Get Ephemerald here (free): https://martinpi.itch.io/ephemerald