| name | zil-implementation |
| description | Implement game logic in ZIL with clean dungeon.zil / actions.zil split, clock daemons, and the critical rules that prevent compilation and gameplay bugs |
Implement game logic in ZIL with clean split between world data and routines.
Inputs
Required Actions
- Implement
dungeon.zil for rooms, objects, and declarative world data.
- Implement
actions.zil for routines, daemon/clock behavior, and GO.
- Implement an executable walkthrough entry.
- Use the engine include chain consistently.
- Apply advanced ZIL patterns where needed (GLOBAL objects, PSEUDO, FDESC/LDESC, PER exits, dynamic descriptions, transformations, daemons).
- Implement one playable vertical slice at a time. After each room, object, puzzle, or NPC interaction, play its exact transcript through
llm.lua before adding the next slice.
- Grow a parser-driven walkthrough test alongside implementation.
Outputs
dungeon.zilactions.zilwalkthrough.zil- Parser-driven walkthrough test under
tests/
Acceptance Checks
- Parser/object/room routines compile and run.
- Puzzle state changes are explicit and traceable.
- Dynamic text and clock events are deterministic enough to test.
- Exact transcript noun phrases parse before and after a save/reload boundary.
- Each completed slice is reachable from a fresh game.
Critical Implementation Rules
0. Never redefine V-LOOK or standard SYNTAX
The substrate (infocom/zork1/) provides V-LOOK and the standard SYNTAX definitions.
0a. Make parser vocabulary explicit
Object IDs and DESC strings are not automatically usable nouns. Every player-reachable object needs explicit SYNONYM and ADJECTIVE entries.
0b. Make containers reveal reachable contents
A printed "open" response is not enough. The world model must change — set OPENBIT, move contents inside.
0c. Guard one-time story progress
If TAKE, READ, and EXAMINE can all reveal a clue, route them through one guarded transition.
0d. Implement ASK/TELL topics for this substrate
ASK ACTOR ABOUT TOPIC and TELL ACTOR ABOUT TOPIC both reach the actor with PRSA = V?TELL. Test <VERB? TELL> and inspect PRSI.
0e. Never redispatch the same action from its default verb routine
PERFORM already dispatches. A default routine must produce the fallback, not call PERFORM again.
0f. Audit parser registration separately from action routines
A V-USE routine does not make the typed verb parse. Add SYNTAX declarations for genuinely new verbs.
0g. Keep puzzle instructions, implementation, and tests identical
For every ordered puzzle, maintain one canonical sequence and copy it exactly into clues, hints, and walkthrough.
0h. Treat titles as modifiers in multiword NPC names
Put the head noun in SYNONYM and titles in ADJECTIVE.
0i. Represent physical world state with objects, not flag-only scenery
Doors, windows, drawers, switches, ropes, vehicles, gates, and containers must be real objects.
0m. Prefer real OBJECTs over PSEUDO for scenery nouns
Every concrete noun in prose must resolve through the parser. The most robust way is a real OBJECT with (FLAGS NDESCBIT ...) — this makes the noun parseable without adding clutter to the automatic room listing. Give scenery OBJECTs generous SYNONYM and ADJECTIVE coverage, and an ACTION routine covering EXAMINE plus any verbs the prose implies (e.g. RUB, SIT, SMELL, LISTEN, READ).
Use PSEUDO only for trivial one-word scenery where the handler does nothing beyond EXAMINE and the word would never need synonyms, adjectives, or state (e.g. "ASHES" → "Cold grey ashes."). Reserve PSEUDO for words that would be confusing as standalone OBJECT names (atmospheric debris, abstract stains, minor surface details). For any scenery noun a player might ask about with a compound phrase ("rusty iron bars"), prefer a real OBJECT — PSEUDO handlers cannot match multi-word descriptions natively and require fragile VOC-EXACT wiring.
NDESCBIT suppresses automatic LDESC listing without hiding the object from the parser. This is the correct pattern for scenery: a parseable noun that does not occupy a room-listing line.
0j. Object ACTION routines must fall through for unhandled verbs
An object ACTION routine is a selective override, not a blanket handler. Return true only inside a branch that actually handles the current verb. Never put an unconditional trailing <RTRUE> after the routine's <COND>: it swallows substrate defaults such as TAKE, DROP, OPEN, CLOSE, LOOK-IN, and SEARCH and can produce silent no-ops. Let unmatched verbs return false so the default verb routine runs. After adding or editing an object action, smoke-test at least EXAMINE plus every applicable generic operation (TAKE/DROP for portable objects; OPEN/CLOSE/LOOK-IN for containers).
0k. Parser reachability is a four-part contract
An authored handler is reachable only when vocabulary, syntax, scope, and flags all agree. Before relying on an object-specific branch, verify:
- every concrete noun used in prose is in the object's
SYNONYM list;
- the standard syntax accepts the intended wording and dispatches the action name tested by the object handler. Trace the exact mapping in
infocom/zork1/syntax.zil: bare CLIMB OBJECT dispatches V-CLIMB-FOO, while CLIMB UP OBJECT dispatches V-CLIMB-UP, so a handler supporting both must test CLIMB-FOO and CLIMB-UP. Adding CLIMBBIT alone does not make CLIMB-FOO match a branch that only tests CLIMB or CLIMB-UP; FIND flags guide implicit-object resolution, not action matching for an explicit noun;
- the object is actually in the room, inventory, containment tree, or room
GLOBAL list where the command is issued;
- conversation topic objects used as
PRSI are in scope in every room where the NPC can be asked or told about them.
0l. Keep prose, topology, and object placement mechanically consistent
Every direction promised by room prose must exist as an exit in that room and lead where the prose claims. Every fixture named as present must be in scope from that room. Audit both sides of every intended two-way connection, and re-check objects mentioned by dynamic room descriptions after moving them.
1. Assign one visible description owner
Use a hybrid object model:
- portable, surprising, and focal objects normally own their automatic
FDESC/LDESC/DESCFCN;
- permanent architectural scenery and spatial relationships may be described by room
LDESC/M-LOOK, with real, GLOBAL, or PSEUDO objects using NDESCBIT for parser affordance;
- stateful prose belongs to one dynamic room action or object
DESCFCN.
Do not repeat the same facts through room prose and an automatic object description. Do not put NDESCBIT on an object whose FDESC is expected to replace text removed from the room. A named noun must parse even when its description is room-owned.
On this substrate, untouched objects with FDESC are printed directly by PRINT-CONT before DESCFCN is consulted. For a stateful object whose automatic listing is owned by DESCFCN, omit FDESC; otherwise the static discovery text shadows the dynamic routine until the object gains TOUCHBIT.
2. Every <TELL> must close with > before the next form
Missing > is the most common and hardest-to-spot bug.
3. Define ROUTINE GO () in actions.zil
The game entry point must exist. Set up HERE, LIT, WINNER, PLAYER, call V-LOOK, call MAIN-LOOP.
4. Custom SYNTAX uses = V-ROUTINE
Only add syntax for verbs absent from the substrate. Search infocom/zork1/syntax.zil first.
5. Bracket balance: every < needs a matching >
8. Custom V-GO direction handlers must mirror every conditional exit
Every conditional exit declared on a room must be replicated inside the matching V-GO routine.
9. NPCs and named objects need generous, overlap-tested vocabulary
Give every NPC role-based synonyms, title adjectives, and ARTICLEBIT.
10. No two objects in overlapping scope may share a DESC
Give every object a unique DESC text and distinct ADJECTIVE.
11. Dynamic room descriptions must faithfully reflect object state
This includes geography and scope: a described eastward route needs an east exit, and a described staircase, container, or other fixture must resolve in that room. After every state change, audit both the room-owned text and automatic object listing for stale or contradictory descriptions.
12. NPC-given items must not be freely TAKE-able before the NPC offers them
13. Pronoun resolution with THIS-IS-IT
After any TELL that names an object, call THIS-IS-IT so the player can refer to it by pronoun.
14. Autonomous NPC movement with clock daemons
15. Mechanical stateful clock daemons
Every mechanical clock daemon must have visible feedback at each stage threshold and interact with EXAMINE on relevant objects.
16. No duplicate portable objects across the world
Each portable item type (knife, key, rope, etc.) must exist as exactly one object instance. Do not implement functionally identical items in multiple locations (e.g. a knife in the kitchen drawer AND a knife in the workshop). If a puzzle requires an item, place it in one reachable location. If the same item type appears in multiple rooms for worldbuilding, either (a) make them distinct objects with different DESC, states, and puzzle roles, or (b) use scenery with NDESCBIT for non-interactive duplicates and document why only one is interactive.
Reference Sources
skills/source_zil_text_adventure_agents.md: section 4skills/source_writing_adventures.md: Game Structure, ZIL Syntax Reference, Advanced Techniques, Complete Example
