Zones, seats and doors

A venue is not one door, and modelling it as one is why most systems cannot answer "can this person be here?".

Gatecrash models it as a graph. That is what makes sequencing possible: perimeter, then concourse, then arena, then the pit — each with its own doors, its own allowlist of which tiers may pass, and its own prerequisites.

Zones

{
  "code": "arena",
  "name": "Arena",
  "kind": "arena",
  "parent": "perimeter",
  "restricted": true,
  "capacity": 2000,
  "shape": [
    { "x": 26, "y": 20 },
    { "x": 94, "y": 20 },
    { "x": 94, "y": 82 },
    { "x": 26, "y": 82 }
  ]
}

Zones nest. Somebody inside the pit is inside the arena and inside the perimeter, which is what lets occupancy be counted at every level from one admission.

restricted is the important one. A tier's grant cascades down the zone tree, so a general-admission ticket granted the perimeter would inherit everything nested inside it — including backstage. restricted stops the cascade, so nesting fails closed rather than open. This was a real bug before it was a flag; see §15 of DECISIONS.md.

capacity is optional and honest: an open field has no meaningful number, and the dashboard only shows an occupancy meter for zones that declare one. For a fully seated zone the compiler fills it in from the seat count, so the two numbers cannot disagree.

Checkpoints

A checkpoint is a door, and it carries everything needed to decide a scan at it:

{
  "code": "pit-gate",
  "name": "Pit Wristband",
  "zone": "pit",
  "direction": "in",
  "policy": "once",
  "requires": ["arena"],
  "tiers": ["vip"],
  "node": "n-pit"
}

• requires — the zones somebody must already have entered. This is the sequencing: a pit wristband scanned before the outer gate is PREREQUISITE_MISSING, refused with a redirect telling the guard where to send them.
• tiers — who may pass at all. Empty means anybody whose entitlement covers the zone.
• sections — narrows a door to specific seat blocks. A stadium vomitory serves one block and nothing else, and a Block A ticket at Portal B is WRONG_DOOR, again with a redirect.
• policy — once, re-entry, or counted with a count_limit. Two drink tokens is a counted checkpoint, and the guard is told "one left" rather than the attendee finding out at the bar.
• direction — in, out or both. An outbound scan removes the zone and everything nested inside it, which is what keeps a capacity meter honest on a room people leave.

Seats

Rows are described the way a real stand is described — a start, an end, a curve and a seat count — and the compiler lays the seats out along a quadratic bezier:

{
  "code": "block-a",
  "name": "Block A",
  "kind": "seated",
  "zone": "arena",
  "entrances": ["portal-a"],
  "rows": [
    {
      "label": "A",
      "start": { "x": 30, "y": 55 },
      "end": { "x": 90, "y": 55 },
      "curve": 4,
      "seats": 12
    }
  ]
}

Writing per-seat coordinates by hand would be both tedious and a second source of truth. A positive curve bows the row left of the direction of travel, which for a row running left to right in front of a stage is towards the audience.

Amenities

Toilets, food, water, medical, exits, charging, cloakrooms. Each has a position and a zone, and the compiler attaches it to the nearest walk-graph node so routing works without you having to say which path leads there.

Marking one accessible is what makes the wallet's step-free search mean something.

Checking a plan

The compiler refuses a plan that does not make sense — a zone cycle, a door in a zone that does not exist, a section whose entrances are not doors into its own zone — and says which line is wrong:

gatecrash-keys inspect manifest.json

The starter plan from gatecrash-keys venue compiles, runs, and contains one of every interesting shape. It is a better starting point than an empty file.

Full field list: Venue plan reference.