Audience: Advanced (comfortable with JavaScript, arrays/objects, data structures)

What this shows

Managing branching logic with a lookup table (state machine) instead of long chains of nested if/else statements — a pattern that scales much better as a story’s branching logic grows.

How it works

• window.setup.moodMachine is a plain object describing every valid transition: for each current state (calm, annoyed, angry, happy), it lists what state each action (provoke, compliment) leads to.
• window.setup.transition(state, action) looks up the current state in the table, then the action within that state, and returns the resulting state (or the original state unchanged if that combination isn’t defined).
• Passages don’t contain any branching logic themselves — they just call window.setup.transition(s.mood, 'provoke') and store whatever comes back. All of the actual rules live in one place (the table), not scattered across passages.

Using this in your own story

1. Model whatever “modes” your story has (an NPC’s mood, a time of day, a relationship level, a quest stage…) as named states.
2. Write a single lookup table describing every valid transition between states.
3. Call a small transition(state, action) helper from your passages instead of duplicating branching conditionals everywhere.

Full source

:: StoryData
{
	"ifid":"2A940332-85B5-4B68-A521-55E933F7A5D3"
}

:: StoryTitle
Finite-State Machine Branching in Snowman

:: UserScript[script]
window.setup = window.setup || {};

// A lookup table describing valid transitions: { currentState: { action: nextState } }
window.setup.moodMachine = {
	calm: { provoke: 'annoyed', compliment: 'happy' },
	annoyed: { provoke: 'angry', compliment: 'calm' },
	angry: { provoke: 'angry', compliment: 'annoyed' },
	happy: { provoke: 'annoyed', compliment: 'happy' }
};

window.setup.transition = function (state, action) {
	var transitions = window.setup.moodMachine[state];
	return (transitions && transitions[action]) || state;
};

:: Start
<% s.mood = s.mood || 'calm'; %>
The NPC's mood is: <%= s.mood %>

[[Provoke them->Provoke]]
[[Compliment them->Compliment]]

:: Provoke
<% s.mood = window.setup.transition(s.mood, 'provoke'); %>
[[Continue->Start]]

:: Compliment
<% s.mood = window.setup.transition(s.mood, 'compliment'); %>
[[Continue->Start]]

Download the .twee file

← Previous: Working with JSON Data · All examples · Next: Custom Events for Notifications →