Overview

Pheno is Townstead’s shared behaviour language, a bit like the cause and effect engine. It describes conditions, actions, selectors, values, capabilities, and runtime context that other Townstead systems can embed.

What Pheno Provides

Area	Purpose
Conditions	Decide whether something is true in the current context.
Actions	Do something in the world, to an entity, to an item, or at a block position.
Selectors	Choose entities or blocks for actions and conditions.
Values	Provide numbers from runtime context.
Gene Nodes	Pheno-backed gene nodes used inside Roots gene files.
Structure	How typed nodes, domains, context, wrappers, authoring rules, and validation fit together.
Context	How Pheno decides the current actor, target, origin, block, item, holder, or cause.
Diagnostics	Report unknown types, malformed fields, and generated reference data for pack authors.

Start with the examples page if you want to see conditions, actions, selectors, and values working together before reading the reference tables.

Where It Appears

Pheno is embedded inside other data formats. The outer file owns the schema field and selects the authoring rules for its nested Pheno blocks.

For example, a gene can use a Pheno action:

{
  "schema": "townstead:gene/v2",
  "type": "pheno:active_ability",
  "cooldown": "10s",
  "do": {
    "type": "pheno:heal",
    "amount": 4
  }
}

A reaction can use a Pheno condition:

{
  "schema": "townstead:reaction/v2",
  "when": {
    "type": "pheno:environment",
    "weather": "clear"
  }
}

Nested Pheno objects do not declare their own schema.