Elm Narrative Engine

A tool for building interactive story games.

Features

Flexible

• No expectations or restrictions on how you build your world model
• View-agnostic

Powerful

• Designed with "salience-based" and "quality-based" narrative systems for immersive and responsive stories
• Advanced querying system

Extendable

• Designed to be used as a "narrative system" component alongside other game code
• Designed with extensible records, making it easy to use the Entity Component System pattern
• Data-driven and declarative - story data can be imported

Usage

See the full working example.

The engine has two main parts: the world model, and the rules.

Define your "World model"

worldModel =
    Dict.fromList
        [ entity "PLAYER"
            |> stat "fear" 1
        , entity "TORCH"
            |> tag "item"
            |> stat "illumination" 7
            |> link "location" "PLAYER"
        , entity "CAVE"
            |> tag "place"
            |> tag "dark"
        , etc...
        ]

Define your rules

rules =
    Dict.fromList
        [ rule "too dark to enter"
            { trigger = MatchAny [ HasTag "place", HasTag "dark" ]
            , conditions = []
            , changes = []
            , narrative = "It's too dark to go in there!"
            }
          )
        , rule "entering the cave with torch"
            { trigger = Match "CAVE" []
            , conditions = [ Match "TORCH" [ HasLink "location" ( Match "PLAYER" [] ) ] ]
            , changes = [ Update "PLAYER" [ SetLink "location" "CAVE", IncStat "fear" 2 ] ]
            , narrative = "You enter the cave, your heart pounding..."
            }
          )
        , etc...
        ]

From there, you can query the world model to build your view, and you can find the best matching rule when a player interacts with an entity given the current state of the world, to update the world and show side effects like story text.

More information

Read the dev blog

Play sample stories made with the Elm Narrative Engine