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CreateReferenceFor authorsApplies from 4.3.0

Conditions

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A condition is data: a string for a flag, an object for the rest, nested with not, all and any. Rules (if), if commands, exits, topics, hints (until), visible, scripts (while, waitUntil), listeners, map news, objectives and checkpoints' goals all take one. Each condition's exact shape is also in the generated DSL reference.

The conditions

ConditionTrue when…
'tied' / '!tied'the flag is true (any value but false, 0, '') / the flag is false or absent.
{ has: 'rope' }the item is in the inventory (a greyed-out used item still counts).
{ flag: 'tries', eq: 3 }the flag holds exactly that value (a number, a string or a boolean).
{ flag: 'tries', gte: 2 }the flag is a number, 2 or more. An absent flag is false.
{ flag: 'x', lt: 5 }the flag is below 5, or is not a number (an absent flag is true).
{ not: … }, { all: [ … ] }, { any: [ … ] }not, and, or.
{ visited: 'market' }the player has already entered the market.
{ room: 'market' }the player is in the market now.
{ prop: ['lamp', 'on'] }, { prop: ['house.lamp', 'on'] }the prop is in that state (in the current room, or 'room.prop'). A prop never changed is in its initial state, else its first.
{ unlocked: 'market' }the place is unlocked on the map.
{ seen: 'topic.ask.basket' }that conversation topic has already been heard (see below).
{ actorIn: ['grandpa', 'house'] }the moving character is in that room (moving characters).
{ player: 'laverne' }this character is the one the player controls now (heroes).

The code is src/engine/core/cond.ts. The Studio's rule explainer shows which part of a condition fails, and why (rule explainer).

{
  "room": {
    "id": "market",
    "name": "The market",
    "decor": "decor/market",
    "actors": { "seller": { "char": "seller" } },
    "props": { "stall": { "name": "stall", "states": { "closed": "market/stall_closed", "open": "market/stall_open" } } },
    "look": { "seller": "The seller.", "stall": "A flower stall." },
    "on": [
      { "id": "market.haggle-done", "verb": "talk", "a": "seller", "if": { "flag": "tries", "gte": 3 },
        "do": [{ "say": ["seller", "Fine. Two coins. Take them and go."] }, { "set": "deal" }] },
      { "id": "market.haggle", "verb": "talk", "a": "seller",
        "if": { "all": [{ "prop": ["stall", "open"] }, { "not": "deal" }, { "any": [{ "has": "coin" }, { "visited": "market" }] }] },
        "do": [{ "inc": "tries" }, { "say": ["seller", "Too low!"] }] }
    ],
    "onEnter": [{ "if": { "flag": "tries", "eq": 2 }, "then": ["One more try. I can feel it."], "else": [] }],
    "hints": [{ "id": "market.hint", "until": "deal", "lines": ["Haggle. Again."] }]
  },
  "layout": {
    "walk": { "area": [[20, 300], [620, 300], [630, 395], [10, 395]] },
    "entries": { "default": [320, 360] },
    "props": { "stall": { "x": 200, "y": 340, "h": 120 } },
    "actors": { "seller": { "x": 420, "y": 350 } }
  },
  "items": { "coin": { "name": "coin", "icon": "items/coin" } },
  "characters": { "seller": { "name": "Seller", "color": "#ffb36b", "sprites": { "idle": ["seller/idle"] } } }
}

seen: what has been heard

{ seen: key } reads the save's record of what happened once: a heard topic, a fired once listener, a picked once option. In a schema 3 game the keys are made from the stable ids (src/engine/core/keys.ts):

ThingKey in schema 3Key without ids (schema 2)
A talk topictopic.<topic id><room>.<actor>.<index> (for example house.grandma.0)
A once listenerevent.<listener id>event.<room or game>.<index>
A once option of a choicechoice.<option id>choice.<room>.<text>

Flags in conditions

A flag holds a boolean, a number or a string (which to use). 'name' tests its truth, { flag, eq } an exact value, { flag, gte } and { flag, lt } a number. Prefer a condition that stays true once true (a flag set once, an item kept) for objectives and goals: the journal never takes a completed objective back (chapters and objectives).

npm run validate reports a flag a condition reads that nothing sets, and a flag set that nothing reads; npm run lint reports a condition that can never be true (cond-never-true).