Items and inventory

Français · Type: reference · Audience: author · Context: engine repository, created project · Status: ready · Applies from: 4.3.0

An inventory item is declared once, in game.ts (items, usually from items.ts), and enters the bag with { gain }. This page gives an item's fields, how the bag works, how items combine, and what a "used" item is.

An item

items: {
  rope: { name: 'rope', icon: 'items/r1c2', look: 'A length of rope. One end for the hook, one for the bucket.' },
},

An item can also be shown in a room as a prop (an image with a name, hidden once taken with visible: { not: { has: 'talkie' } }): the prop and the item are two things, joined by the rule that takes it ({ hide: 'bucket' }, { gain: 'bucket' }).

The bag

• The game starts with start.inventory (game.ts); a checkpoint names its own (checkpoints.<id>.inventory).
• { gain: 'rope' } adds an item (once: gaining an item already held changes nothing), { lose: 'rope' } removes it.
• { has: 'rope' } tests it (conditions).
• Tapping an item with no verb picked selects it for Use; the sentence line says "Use rope with …" and the next tap names the target. With a double tap on a target, an item picked from the bag is given to a character and used on anything else (reactions).
• Several playable characters each have their own bag unless players.sharedInventory; { transfer } hands an item over (heroes).

Combining and giving

"Use A with B" and "Give A to B" are rules with a the item and b the target. Two inventory items combine both ways: a rule a: 'left_half', b: 'right_half' also answers "Use right half with left half" (only when both are held). Rules valid everywhere, combining two items for instance, go in the game's rules.on. With no rule, "Use A with B" answers with the use2 fallback lines, and "Give" to a character with their refuse line (reactions).

A used item

{ used: 'rope' } (or a list) says the item has served its purpose: it stays in the bag, greyed out, and can no longer be picked for Use or Give (Look still works). It becomes active again wherever a room or game rule targets it in a or b and that rule's if condition is true. So keep the rule that consumed it behind an if (here '!tied'), otherwise it stays active in that room. gain on a used item reactivates it. The used list is saved; older saves load without it.

{
  "room": {
    "id": "well",
    "name": "The well",
    "decor": "decor/well",
    "hotspots": { "hook": { "name": "hook" } },
    "look": { "hook": "A rusty hook over the well." },
    "on": [
      { "id": "well.tie-rope", "verb": "use", "a": "rope", "b": "hook", "if": "!tied",
        "do": [{ "set": "tied" }, { "used": "rope" }, "Tied. The rope hangs down the well."] }
    ],
    "hints": [{ "id": "well.hint", "until": "tied", "lines": ["The rope. The hook."] }]
  },
  "layout": {
    "walk": { "area": [[20, 300], [620, 300], [630, 395], [10, 395]] },
    "entries": { "default": [320, 360] },
    "hotspots": { "hook": { "rect": [300, 120, 40, 40], "approach": [320, 330] } }
  },
  "items": {
    "rope": { "name": "rope", "icon": "items/rope", "look": ["A length of rope.", "Still a rope."], "kind": ["tool"] }
  }
}

Limit · used-is-not-lost A used item still counts for { has }. To make it leave the bag, lose it; to test that it was used, set a flag in the rule that used it.

The hint item

hintItem in game.ts names an item that gives hints when talked to (the demo's walkie-talkie, the template's note); hintVoice names the character who says them, often an offscreen one. Talking to it gives the current room's first hint whose until is still false (rooms: hints). The validator refuses a hintItem that is not an item.

Related identifiers

• ItemDef in src/engine/core/types/content.ts; gain, lose, used, transfer (commands); { has } (conditions).
• npm run lint reports an item never gained (item-never-gained) and a red herring nothing uses (item-red-herring) (checking your game).

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