THRESHOLD — Gameplay Specification

Choice-Based MUD & Multiplayer Cooperation Capability Module — KN-86 Deckline

Version 1.0 | April 2026 | Status: Engineering-Ready

CIPHER-LINE revision note (2026-04-24): Threshold’s Cipher voice — room atmospheric fragments, NPC observation, party-status notes, quest beats — renders on the CIPHER-LINE OLED, not the main 80×25 grid. Critically, Threshold’s room descriptions, NPC dialogue, and item text are main-grid content authored by the cart — NOT Cipher utterances. Cipher’s role in Threshold is peripheral ambience: it drifts while the operator reads, observes significant events, and echoes past explorations. Party mode: both operators see independent CIPHER-LINE outputs (Cipher voice is deck-local, not networked); coherence stacks are deck-local. See the CIPHER-LINE Contributions section at the end. Canonical engine spec: docs/software/runtime/cipher-voice.md.

Mission Contributions

Mission Composition Grammar declaration — verb vocabulary, affinity tag set, and mission-contributions schema are defined in docs/plans/post-v0.1/2026-04-25-mission-composition-grammar.md §1–§3.

(mission-contributions
  :verbs (NEGOTIATE OBSERVE OBTAIN COMMUNICATE)
  :affinities (SOCIAL PHYSICAL IDENTITY))

Threshold is the launch library’s only NEGOTIATE and only SOCIAL satisfier (called out as such in addendum §1 and §2). NPC dialogue and party-roles negotiation satisfy NEGOTIATE; room exploration and INFO scans satisfy OBSERVE; item collection satisfies OBTAIN; party-mode coordination and NPC outreach satisfy COMMUNICATE. Affinities are SOCIAL (interpersonal exchange is the core fiction), PHYSICAL (the city core and wilderness have spatial extent), and IDENTITY (operator handle, party-roles persona, NPC trust relationships — the party-roles subset noted in addendum §2). Default biases. Until the concept-cart library expands (HOSTILE TAKEOVER, CLONESHOP, GHOSTLINE), Threshold is the sole carrier of NEGOTIATE / SOCIAL / IDENTITY in the launch library — see addendum §1 + §2 and the coverage caveats noted in this PR.

Design Philosophy

THRESHOLD is not a menu-driven choice game with Lisp verbs bolted on. It is a navigable text world accessed through genuine Lisp list structure — where the KN-86’s CAR/CDR keys are not metaphors but literal operations on a nested hierarchy of locations, NPCs, items, and quests. The operator’s mastery arc follows the PERCEPTION-ORIENTATION-DECISION-ACTION (OODA) loop at a measured tempo (exploration cycles: 5-15 seconds; combat cycles: 8 seconds per turn), making THRESHOLD a deliberate, contemplative adventure rather than a reflex-driven challenge.

The core fantasy is exploration without a map. You arrive in darkness — a room you’ve never seen. The Threshold interface tells you there are exits, NPCs, items. You orient yourself with INFO (look around), then act: ENTER (drill into a doorway), NEXT (move to the adjacent room), COMBINE (combine items or negotiate with an NPC). Mastery feels like understanding the world’s structure at a deeper level — which rooms connect to which, which NPCs trust you, which item combinations unlock hidden paths.

Multiplayer-first architecture is the design’s soul. Two operators with complementary roles (scout/negotiator, risk-taker/cautious) navigate a handcrafted city core plus infinite procedural wilderness. Party-based content (dual-lock puzzles, synchronized combat, cross-operator quests) requires cooperation. Solo play is possible and satisfying (70% of depth) but pale compared to linked exploration. The world scales with party size, not down from it.

Publisher: Pacific Rim Dynamics — a maritime-signal-processing collective that treats the digital network as a shared commons. This distinguishes THRESHOLD’s exploratory tone from ICE BREAKER’s corporate espionage aesthetics.

1. Executive Summary

THRESHOLD is a choice-based MUD accessed through the Lisp key interface, optimized for multiplayer-first party play. Two operators with complementary roles navigate a handcrafted city core (Threshold City, 35–45 rooms) plus procedurally generated wilderness and dungeons. The deck’s 31 keys become verbs; the terminal becomes a window into an interconnected network of rooms, NPCs, and mysteries.

Core Loop:

15-min session: Arrive in an unfamiliar hub, ENTER buildings, NEXT between adjacent rooms, talk to NPCs, pick up items.
60-min session: Complete a multi-stage quest through a chain of rooms and puzzles.
2-hour session (multiplayer): One operator scouts wilderness independently (async); the other negotiates with NPCs. They reunite for synchronized puzzles (dual locks, pressure plates). Complementary roles create moments neither could accomplish alone.

Three Biggest Design Choices:

Lisp list navigation as the entire interaction model. CAR/CDR/CONS are not menu verbs — they’re genuine list operations mapped to rooms, inventory, and NPC dialogue. Rooms are nested lists. Mastery feels like learning the structure of the world, not memorizing interface shortcuts. On-screen verb hints (e.g., “[ENTER: drill in]” instead of “[CAR: enter]”) teach domain meaning without jargon.
Hybrid async/sync multiplayer. 70% of content and 100% of core gameplay is solo-playable. 30% (cross-operator puzzles, synchronized quests, complementary roles) is multiplayer-exclusive. Exploration is async (operators in different zones simultaneously); combat and puzzles are sync-required (both operators in same room, both confirming via EVAL). A robust sync protocol with error recovery handles cable disconnections and latency gracefully.
Early coop hook by minute 20. The first 30 minutes are explicitly designed to give new operator pairs a “we did something together that neither of us could do alone” moment (the dual-lock vault puzzle at minute 15–20), establishing multiplayer as essential rather than optional.

2. Diegetic Premise & Fiction

The Kinoshita KN-86 has just dialed into THRESHOLD, a persistent text-based network operated by the Cartographers’ Guild — a loose academic/anarchist confederation mapping the digital underground, treating the network as a shared commons. This is not a rogue AI collective; the Guild maintains the infrastructure carefully, as stewards of a shared resource.

The network is accessible only through specific terminals (your deck is one). Other operators are connected simultaneously. The world is real (within the fiction), and your presence in it affects the environment. You have a handle (your operator identity), an implied avatar, an inventory, relationships with NPCs, and debts to settle. The cartridge is not a game client — it is your actual connection to the network. Disconnecting logs you out. Logging back in hours later finds the world evolved: NPCs have moved, quests have progressed, dungeons remain cleared (treasure doesn’t respawn).

This is the fiction that justifies why a MUD on a cartridge is not simply a menu-driven choice game — it feels like you’re really connecting somewhere.

3. Core Fantasy & Player Promise

What does the operator feel?

Exploration without a map. You arrive in darkness — a room you’ve never seen. The Threshold interface tells you there are exits, NPCs, items. You orient yourself with INFO (look around), then act: ENTER (drill into a doorway), NEXT (move to the adjacent room), COMBINE (combine your rope with the hook on the wall), COMMIT (drink the potion and descend into the pit). There’s no inventory screen in the traditional sense — you navigate a mental space and manipulate objects as nested lists within it. Mastery feels like understanding the world’s structure at a deeper level.

Over time, the fiction becomes real. You recognize NPC names. You remember that the wizard in the Library wants the Crimson Ledger from the Vault. You know the shortcut through the swamp. The world acquires texture.

In multiplayer, the texture deepens: your co-operator has made different choices, known different NPCs, learned different routes. When you link up, you’re not cooperating mechanically (passing the controller) — you’re meeting in a shared space, each bringing unique knowledge. Complementary roles emerge naturally: one of you is the negotiator, the other the scout. One reads the runes, the other picks the locks.

The session rhythm swings between idle exploration (poking into new corners, trying keys on locked doors) and crescendo moments (you finally gather all the pieces of a multi-stage quest, the pieces snap together, you COMMIT and something changes forever).

A 15-minute session: Arrive in an unfamiliar town, ENTER the inn, NEXT between rooms, talk to an NPC who offers a task. Two hours: Complete that multi-stage task through a chain of rooms and puzzles, unlock a new zone, discover something that recontextualizes earlier encounters, feel the weight of choice.

4. Lisp Verb Mapping & Grammar

Analysis Against Existing Paradigm

The Lisp Paradigm Revisions document establishes that CAR = drill/descend, CDR = traverse/sibling, CONS = construct/combine, NIL = discard/cancel, APPLY = execute stored function. These are not arbitrary — they map to genuine list structure. Every module honors this core semantic.

For a MUD, the natural mapping:

CAR (ENTER) = Enter a room (descend into the next context in a nested list of locations)
CDR (NEXT) = Move to adjacent room (traverse siblings in the current depth)
CONS (COMBINE) = Construct new state (combine items, prepare NPC offer, secure rope to hook)
NIL (CLEAR) = Discard/cancel (drop an item, exit conversation, reset puzzle attempt)
APPLY (EXECUTE LAMBDA) = Execute a recorded sequence (replay a macro at a new door)
EXAMINE (new) = Deep inspection of a single object (read scroll, talk NPC at length, analyze trap)

The list structure is identical across modules; the domain vocabulary differs. This is the design working as intended.

Final Verb Map for Threshold

Function Key	Threshold Verb	Domain Action	Lisp Semantic	On-Screen Label	Notes
CAR	ENTER	Step through a doorway into the next room	Descend into location list HEAD	ENTER: drill into	If room has no exits, beep. Numpad 8/2/4/6 for direction.
CDR	NEXT	Move to adjacent room (sibling in current zone)	Traverse location list REST	NEXT: sibling room	Move through rooms at same hierarchy level. Wraps at edges.
CONS	COMBINE	Construct new state: combine items OR prepare NPC offer OR secure rope to fixture	Construct new pair	COMBINE: [context]. “Combine items?” / “Prepare offer?” / “Secure rope?”	Context-aware hint disambiguates. Always construction semantics.
NIL	CLEAR	Drop held item, abandon conversation, reset puzzle attempt	Return to empty/null state	CLEAR: drop or cancel	Safe to use repeatedly. No destructive side effects.
ATOM	ATOMIC?	Test if current object can be drilled further (is container/NPC/puzzle or simple item)	Test list membership	[context-aware label]	Feedback on whether ENTER will work.
EQ	COMPARE	Compare current object with QUOTE’d reference (find duplicates, detect changes)	Test element identity	[not displayed, implicit]	Useful for quest objectives.
EVAL	COMMIT	Execute the prepared action (drink potion, enter room, attack NPC, start quest)	Evaluate quoted data → action	[COMMIT: execute]	Irreversible. Operator confirms intent via exploration first.
QUOTE	BOOKMARK	Mark a location, NPC, or item for later reference (3 concurrent bookmarks)	Quote: defer evaluation, hold as data	BOOKMARK	Navigate away, QUOTE later to jump back.
LAMBDA	MACRO	Record a sequence: “check lock, look around, try key” — replay at other doors	Define function for APPLY	[MACRO: record]	Persists across cartridge swaps.
APPLY	EXECUTE	Execute a stored LAMBDA sequence against a new target	Apply function to data	[EXECUTE MACRO]	Universal semantic: replay stored procedure.
EXAMINE	INSPECT	Deep inspection of an object (read scroll, talk NPC at length, analyze trap)	Focused atomic analysis	EXAMINE [object]	Threshold-specific. Shows full object state. Screen-off: audio narration via Cipher. Key binding: F10.
BACK	RETREAT	Return to the previous room	Pop navigation stack	RETREAT	Footsteps sound. Breadcrumb tracked.
INFO	SCAN	Look at current room (exits, visible items, NPCs present)	Non-destructive observation	SCAN	Always available. Does not change room state. Screen-off: audio narration.
LINK	SUMMON	Call your linked co-operator into your current room (if in same zone)	Inter-cartridge linking	[SUMMON]	Multiplayer-only. Optional convenience.
SYS	MENU	System menu (save, load, inventory, knowledge, stats, disconnect)	Firmware-level access	MENU	Tap = menu, hold 2s = hard quit.
Numpad 1–8	SELECT	When a choice menu appears (NPC dialogue, puzzle solutions), numpad selects	Context-dependent selection	[numpad hints]	Only active during choice prompts.
Numpad 0, +, −, ×, ÷, .	INPUT	Secondary options or numeric data entry (damage rolls, inventory amounts, cipher digits)	Context-dependent numeric	[input prompt]	Module-specific usage.
PAD_ENTER	CONFIRM	Confirm numpad entry (password, trade amount)	Commit numeric input	[CONFIRM]	Terminates numpad input mode.

Collision Analysis & Auditing

Actual Collisions Resolved:

CONS overloading (item combination vs. NPC trade): RESOLVED via context-aware on-screen hints. Both operations construct new state, so the verb is unified. The UI clarifies which domain is active.
APPLY overloading (LAMBDA execution vs. object inspection): RESOLVED by introducing EXAMINE as a dedicated verb for deep object inspection. APPLY is reserved exclusively for LAMBDA execution (universal semantic across modules).

Verb Collision Audit Table (Cross-Module):

Verb	ICE Breaker	DEPTHCHARGE	THRESHOLD	SHELLFIRE	Collision?
CAR	Drill network node	Drill depth layer	Enter room	Enter freq band	✓ Coherent (all = descend)
CDR	Traverse ICE	Move between wrecks	Move to sibling room	Switch freq bands	✓ Coherent (all = traverse)
CONS	Build exploit chain	Combine cargo	Construct item/offer/state	Combine bypass methods	✓ Coherent (all = construct)
NIL	Clear trace	Exit wreck	Clear/drop/cancel	Reset band analysis	✓ Coherent (all = null/empty)
APPLY	Execute stored exploit	Replay extraction sequence	Execute LAMBDA macro	Deploy countermeasure pattern	✓ Coherent (all = execute)
EXAMINE	Inspect node properties	(N/A—APPLY used)	Inspect object deeply	(N/A—context varies)	✓ Threshold-specific, no collision

5. Capability Model Integration

Universal Deck State Integration

THRESHOLD correctly reads and writes:

credit_balance — quest payouts, equipment costs, NPC trades
reputation — quest completion, moral choices, NPC relationships
cartridge_history bitfield — cleared dungeons, cross-module unlocks
cipher_seed — procedural wilderness seeding (deterministic per operator pair)
knowledge_index — learned facts affecting puzzle difficulty and alternate solution paths

Mission Board Integration

THRESHOLD registers mission templates with the nOSh runtime. The mission board generates contracts from cartridge-provided templates seeded by deck state. Multi-phase contracts span multiple capability domains, requiring physical cartridge swaps (e.g., Threshold Phase 1 → Black Ledger Phase 2 → Threshold Phase 3).

Phase Chain Handling

Multi-phase quests are correctly routed through nOSh runtime managed phase_chain. The Cipher voice tracks phase progression and provides diegetic narrative continuity.

World Persistence Model

How does the procedural wilderness remember state?

Dungeon-cleared state is GLOBAL and persists. When you clear a procedural dungeon (e.g., “Dark Cavern at coordinates E3”), the cartridge marks that location as cleared in the Universal Deck State’s cartridge_history bitfield.
All operators see the same cleared state. Operator A clears Dark Cavern on day 1. Operator B inserts Threshold on day 5. Operator B navigates to Dark Cavern and sees it cleared (treasure gone, NPCs gone). The world is shared.
Linked operators merge clears. When two operators link and explore together, both see both operators’ previous clears. When they unlink, both retain the merged history (union, not conflict). Example: Operator A previously cleared Cavern A. Operator B previously cleared Cavern B. They link, explore Cavern C together, unlink. Both now see A, B, and C as cleared.
NPC state persists per-operator. NPCs remember being helped/betrayed. This is stored in the cartridge’s save data (per-NPC relationship flags). The state is not shared across operators; it’s per-operator reputation. But if Operator A helps NPC_X, that relationship is locked in Operator A’s cartridge forever.
Items and treasure. Once cleared, treasure is gone from a dungeon for all future visits by all operators. Respawning is off.

Consequence: The world feels alive and shared, not randomly generated per session. Your choices matter and persist globally.

6. World Architecture

Overview

Threshold’s world is hybrid: a handcrafted hub region (the city of Threshold itself) plus critical-path locations, plus vast procedurally generated wilderness and dungeons beyond the safe zone.

Design philosophy:

Handcrafted = every room has personality, every NPC is named and remembered
Procedural = infinite exploration potential, each session discovers new territory
Procedural seeded by cipher_seed = two decks with identical deck state generate identical wilderness, enabling shared expeditions

The Handcrafted Core: Threshold City

Scope: 35–45 hand-authored rooms forming a contiguous urban grid plus key interior spaces (Inn, Temple, Market, Guard Post, Archive, Smithy).

Explicit Room Hierarchy (New in Final Spec):

THRESHOLD_CITY (root)
├── MARKET_SQUARE (hub, level 1)
│   ├── MERCHANT_STALL (interior, level 2)
│   ├── INN (interior, level 2)
│   │   ├── GUEST_ROOM_1 (interior, level 3)
│   │   ├── GUEST_ROOM_2 (interior, level 3)
│   │   └── BACK_ROOM (interior, level 3, unlocked late)
│   └── ARMOR_SHOP (interior, level 2)
├── TEMPLE_QUARTER (hub, level 1)
│   ├── TEMPLE_EXTERIOR (level 2)
│   ├── ALTAR (level 2)
│   └── CRYPTS (level 2, dungeon entrance)
├── ARCHIVE (hub, level 1)
│   ├── LIBRARY_MAIN (level 2)
│   └── RESEARCH_ROOM (level 2, restricted)
├── DOCKS (hub, level 1)
│   ├── HARBOR_MASTER (NPC room, level 2)
│   └── BOAT_DOCK (level 2)
├── SLUMS (hub, level 1)
│   ├── BEGGAR_QUARTER (level 2)
│   └── UNDERWORLD_DEN (level 2)
└── SMITHY (hub, level 1)
    └── FORGE (level 2)

CAR/CDR Rules:

CAR: Drill from Market Square → Inn. Descend one level in the tree.
CDR: From Inn, CDR → Armor_Shop (both level 2, both children of Market Square). Move to next sibling.
Procedural wilderness: Biomes are level 1 (Forest, Mountain, Swamp, etc.). Rooms within a biome are level 2 (Clearing 1, Clearing 2, etc.). CDR cycles through clearings.

Key Locations

Market Square (central hub) — Commerce, quests, rumor-gathering
The Wanderer’s Rest (Inn) — Lodging, information, tutorial NPC (KEEPER)
Archive (knowledge hub) — Books, research, knowledge acquisition
Smithy (upgrades) — Equipment repairs, item crafting
Guard Post (law, bounties) — Faction quests, law enforcement
Temple (lore, blessings) — Spiritual guidance, blessing mechanics
Docks (sea travel) — Alternative escapes, merchant routes
Slums (alternate solutions) — Black market, morally ambiguous quests

Handcrafted Critical Path

A multi-phase arc through the core world:

Art 1 (0–30 min): Learn controls, meet KEEPER, complete first independent exploration, solve early dual-lock puzzle.
Art 2 (30–90 min): Follow main quest thread (retrieve a stolen artifact from a rival faction), meet key NPCs, establish faction relationships.
Art 3 (90–180 min): Navigate a conspiracy spanning multiple factions, make moral choices that lock your reputation alignment.
Art 4 (180–240 min): Reach the climactic confrontation (the artifact’s true purpose, the conspiracy’s architect revealed).
Art 5 (240+ min): Post-game: open-ended exploration, optional side quests, high-reputation contracts, procedural wilderness mastery.

Procedural Wilderness

Biomes (Forest, Mountain, Swamp, Underground, Coastal) generate procedurally using the cipher_seed. Within each biome:

Terrain: Natural hazards (cliffs, water, toxic gas)
Enemies: Tier-scaled encounters (1 spider in Forest shallow, 5 bandits in Mountain deep)
Treasure: Loot tables scaled to depth and biome
Encounter NPCs: Merchants, refugees, hidden treasures guarded by puzzles

Biome structure is deterministic and learnable: Forest always has a stream network; Mountains always have a high pass. Operators can build mental maps.

7. Core Loop

15-Minute Session

Minute 0–3: Arrive in Market Square (or select from BOOKMARK menu if returning). Cipher voice: “Welcome back to Threshold. What brings you to the network today?” You see the status bar: “[LINKED: None]” if solo, or “[LINKED: PARTNER ✓]” if paired.

Minute 3–10: Independent exploration. ENTER a building (the Inn). NEXT through rooms. Find an NPC. EXAMINE them to trigger dialogue. Pick up items (rope, wineskin). Build familiarity with a single zone.

Minute 10–15: Encounter a puzzle or quest hook. “A merchant wants rope in exchange for information.” COMBINE your rope with the merchant’s request. COMMIT to execute the trade. Gain reputation +5, learn a fact about a deeper mystery.

Exit condition: You’re curious about the next zone. You promise yourself to come back tomorrow.

60-Minute Session

Minute 0–20: Boot, orient, complete early quests (gather 3 items scattered across Market Square and Temple Quarter).

Minute 20–45: Travel to a new zone (Archive or Docks). Encounter a more complex NPC relationship (a scholar who wants a rare book in exchange for a password). Navigate to the book’s location (Library interior). EXAMINE the book for context. Return and execute the trade.

Minute 45–60: Use the password to unlock a room. Encounter a multi-step puzzle (a cipher requiring knowledge from a previous session, OR a physical puzzle: moving levers in a specific sequence). Solve it. Reward: rare item, reputation +25, unlock to a new zone or NPC relationship.

Exit condition: Momentum. You’ve completed a quest arc and earned something. You feel progression.

2-Hour Session (Multiplayer)

Minute 0–15: Boot, link, orient in Market Square together. Tutorial NPC (KEEPER) explicitly teaches controls (both operators learn in parallel).

Minute 15–30: Split up. Operator A scouts wilderness (northeast Forest) collecting resource nodes. Operator B negotiates with NPCs in Market Square, gathering intelligence on a deeper quest.

Minute 30–50: Reunite. Compare notes. “I found a map fragment.” “I learned that the map leads to the Lost Temple.” Together, plan the expedition.

Minute 50–75: Navigate together through Temple Quarter to the temple entrance. Encounter a pressure-plate puzzle (both operators must press simultaneous plates to open a door). COMBINE to activate plates. COMMIT simultaneously (sync check ensures both ready). Door opens. Both get +25 rep, rare artifact.

Minute 75–120: Continue deeper into procedural wilderness (async). Scout ahead (fast movement). Negotiate with NPCs (slower). Reunite for a combat encounter (linked combat: sync-locked 8-second turns, both taking turns alternately). Victory grants shared rewards.

Minute 120–150: Explore deeper zones discovered during independent play. Unlink intentionally. Both retain merged dungeon-cleared state and reputation.

Exit condition: Two operators have shared an adventure. They changed the world together. They plan the next expedition.

Onboarding and Early Coop Hook (New in Final Spec)

Goal: By minute 20, a new pair of operators (one experienced, one new) have experienced at least one moment where “we did something together that neither of us could do alone.” This is the hook that makes multiplayer feel essential.

Minute 0–5: Boot, Link, Orientation

Both operators boot their decks, link via TRRS cable.
Firmware handshake. “THRESHOLD SYNCHRONIZED. CIPHER_SEED: 0x7A9F. BOTH OPERATORS IN SHARED INSTANCE.”
Both arrive in MARKET SQUARE. Status bar shows “[LINKED: PARTNER_NAME ✓]”
Cipher voice greeting: “Welcome to Threshold, operators. You are meeting in Market Square. Prepare to navigate the network.”

Minute 5–10: Tutorial with Keeper NPC

Experienced operator guides: “Let’s go to the Inn.”
Both ENTER (CAR) the Inn. NEW OPERATOR encounters dialogue from KEEPER.
KEEPER (diegetic tutor): “First time on the network? Let me teach you the interface. Press ENTER to explore a room. (Example: ENTER the back room.) Press NEXT to move between nearby rooms. Press COMBINE to work with an object or another person. Press COMMIT to execute your action. Watch me demonstrate.”
Scripted sequence: Keeper guides each verb with live examples. “Now you try. Press ENTER on that door.” New operator presses CAR + numpad 8. Door opens. “Good. You’ve entered deeper into the network. Press NEXT to explore adjacent rooms.” Etc.
Emotional beat: New operator feels guided, not lost. Keys are being taught in context, not as abstract Lisp jargon.

Minute 10–15: First Independent Exploration (Solo in Different Zones)

Experienced operator: “Let’s split up and find clues. I’ll talk to the Quest-Giver. You explore the area.”
Experienced operator stays in MARKET SQUARE, talks to QUEST-GIVER via COMBINE (NPC interaction).
New operator explores TEMPLE_QUARTER (via ENTER + NEXT).
Each operator discovers half of a two-part quest: “A sealed vault requires two keys. One key is hidden in the Temple, guarded by a puzzle. The other key is held by the Merchant’s Guild.”

Minute 15–20: FIRST COOP MOMENT — Dual-Lock Puzzle

Both operators reunite at the vault entrance (in a shared room).
The vault has two key slots, side-by-side. Above them: “TWO KEYS REQUIRED. INSERT SIMULTANEOUSLY.”
Experienced operator enters the Temple and retrieves Key A. New operator negotiates with Merchant guild and retrieves Key B.
Both return to the vault.
Puzzle mechanic:
- On-screen prompt: “Sync check: PARTNER ready? [CONFIRM]” Ensures both operators are present and cable is stable.
- Countdown appears: “Inserting keys in 3… 2… 1…”
- Both operators COMBINE (CONS) their key with the lock (context hint: “[COMBINE: insert key into slot]”).
- Both COMMIT (EVAL) simultaneously.
- If both succeed: Vault opens. Both get +5 reputation. Shared reward (item inside benefits both).
- If one fails or disconnects: Puzzle resets. Error message guides retry.
Emotional beat: NEW OPERATOR feels essential. The experienced operator couldn’t open the vault alone (would require finding both keys solo or forgoing the vault). By splitting effort, they both contributed. They are now partners, not just playing near each other.
Cipher voice: “VAULT OPENED. PARTNERSHIP SYNCHRONIZED. BOTH OPERATORS GAIN REPUTATION.”

Minute 20–30: Follow-Up Momentum

Inside the vault, a rare item and a clue about a deeper mystery.
NEW OPERATOR asks: “That actually worked.”
EXPERIENCED OPERATOR: “Yeah. This is why multiplayer is better than solo.”
Both leave with momentum and a sense of “there’s more to explore.”

Optional Scripting: If the experienced operator already knows Threshold, they can deviate from this script. But the script is available as a default first-time path.

8. Mechanics

ENTER (CAR): Drill into a doorway (or into a container, NPC dialogue tree, or nested interface). Pressing CAR opens a numpad menu (8/2/4/6 for cardinal directions, or implicit if only one exit).

NEXT (CDR): Move to an adjacent room at the same hierarchy level. Rooms are arranged as siblings in a tree. CDR cycles through them (wraps at edges). Example: From Inn, CDR → Armor Shop (both level 2 children of Market Square).

RETREAT (BACK): Return to the previous room. Breadcrumb navigation stack (max 10 rooms). Footsteps play (YM2149 audio signature).

SCAN (INFO): Look at the current room without changing state. Shows exits, visible NPCs, visible items, hazards. Does not trigger events. Available at any time.

BOOKMARK (QUOTE): Mark a location for later return. Up to 3 concurrent bookmarks. QUOTE again at the marked room to jump back (teleport, instant, diegetically: “You trace your path from memory”).

8.2 Inventory & Item System

Working Inventory: Operator can carry up to 10 items. Inventory persists across sessions (stored in save data). Items have properties: type (tool, consumable, artifact), weight, value, combination triggers.

Item Combination and Decombination (New in Final Spec):

CONS creates a new item from two originals. The original items are consumed (gone from inventory).
Example: You have Rope and Hook (2 separate inventory slots). You COMBINE them (CONS). Rope and Hook disappear. A new item, Grappling Hook, appears in your inventory.
Consequence: You can no longer use Rope or Hook separately. They are permanently merged into Grappling Hook. To get Rope back, you must:
- Find another Rope (loot, NPC trade, quest reward), OR
- CONS Grappling Hook + Scissors → separate back into Rope + Hook (reversible if you have Scissors).

Puzzle Design Implication: If a puzzle requires “Rope AND Hook simultaneously,” the operator must have two copies of Rope, OR not combine them, OR find a different approach. This constrains combo chains but creates interesting resource-management puzzles.

8.3 NPC Dialog

NPCs are named individuals with relationship states (stranger, acquaintance, ally, enemy, romantic interest). NPCs have dialogue trees (triggered by COMBINE) with branching options.

Dialogue Flow:

COMBINE to initiate dialogue (context hint: “[COMBINE: talk to NPC_NAME]”).
Cipher voice enumerates options: “[1] Rest at the inn — costs 5 credits, restores health. [2] Hear the news. [3] Goodbye.”
Operator presses numpad (1/2/3) to select.
Result: dialogue branch plays out. Reputation changes. Quests unlock.

Dialog Persistence: Relationship state (conversation history, quests accepted, items traded) persists in save data. Returning NPCs remember you.

8.4 Combat

Combat Trigger: Encountering an enemy (either player-initiated via COMBINE with a threat, or random encounter in wilderness).

Combat Loop (Turn-Based, Real-Time Pressure):

Turn length: 8 seconds per turn (timer visible on screen).
Actions available per turn: COMBINE (use item or attack), RETREAT (flee), SCAN (observe), or wait (do nothing).
Health model: Both operator and enemy have health (e.g., 50 HP each). Combat ends when one reaches 0 (death) or operator chooses RETREAT (escape with reputation -2).
Accuracy & Damage: Attacks have accuracy % (60-90% depending on weapon and enemy). Damage ranges (d6 for light weapon, d10 for heavy weapon). Some enemies have special abilities (stun, poison, disarm).

Linked Combat (Both Operators Present):

Sync-locked turns. Operator A attacks, Operator B attacks, Enemy attacks. 8 seconds per full round (3 actions).
Both operators’ damage stacks. Combined advantages (healing item, buff from one operator extends to both).
Reputation gains apply to both.

Solo Combat (One Operator, Other Elsewhere):

Turn-locked to solo operator’s tempo (8s per turn). Partner sees notification: “PARTNER_NAME is in combat with Shadow Drake.”
Reputation changes are LOCAL (don’t affect partner until resync).

8.5 Quests

Quest Types:

Fetch: Retrieve an item and return to NPC (10-30 min sessions).
Escort: Guide an NPC from Point A to Point B, defending against enemies (20-40 min).
Investigation: Gather information from multiple NPCs, piece together a conspiracy (30-60 min).
Multi-Phase: Chain of 3-5 quests unlocking each other (spanning 90+ min).

Quest Tracking: SYS menu shows active quests with objectives, progress, and NPC contact info. Completed quests grant reputation and credits.

8.6 Progression System

Reputation: 0-500 scale. Affects NPC dialogue options, difficulty scaling, special quest unlocks. Gained by quest completion (+5 to +50 per quest). Lost by evil choices or combat defeats (-2 to -10).

Credits (¤): Currency for NPC trades, equipment repairs, lodging. Earned by quest completion. Economy self-corrects via inflation scaling (expensive items cost more as credits accumulate).

Knowledge and Learning Progression (New in Final Spec):

How does the knowledge system work?

Learning triggers: Reading a book in the Archive, talking to an NPC at length (EXAMINE), solving a puzzle for the first time.
Knowledge acquisition: When you learn something, Cipher voice narrates: “KNOWLEDGE ACQUIRED: Cipher rotation pattern. Numbers shift by 3 daily.”
Knowledge storage: Lives in knowledge_index (Universal Deck State, shared across cartridge swaps).
Knowledge visibility: SYS menu includes a “KNOWLEDGE” submenu. You can review all learned facts in a searchable list.
Knowledge effect: Each learned fact grants +10% speed for related puzzles. Example: “You know ‘Cipher rotation pattern.’ Cipher puzzle difficulty: MODERATE (normally HARD). Estimated solve time: 30 seconds (normally 1 minute).”
Alternative paths: Some puzzles can be skipped if you have the required knowledge. Example: “To unlock the library seal, you need ‘Library password’ knowledge OR solve a 2-minute puzzle.” Having learned the password, you can skip the puzzle.
Feedback: When knowledge helps, Cipher announces it: “Your knowledge of Cipher patterns lets you decode this quickly.”

Design philosophy: Knowledge isn’t invisible progression. It’s explicitly tracked, reviewable, and mechanically rewarding.

9. Multiplayer-First Party Play

9.1 The Differentiator

Threshold is not multiplayer-compatible. It is multiplayer-first. The design assumes two operators, degrades gracefully to solo, and shines in linked play.

Why multiplayer-first matters:

Cross-operator puzzles (pressure plates, dual locks) are designed for two simultaneous actors, one per role.
Complementary roles (scout/negotiator) emerge from asymmetric information (operators explore different areas, share intel).
Async exploration + sync moments create natural rhythm: fast individual phases, slow coordinated phases.

9.2 What Linked Play Actually Feels Like

Imagine: You’re the scout. Your partner is the negotiator.

Minute 30–45: You split. You dash through the Forest, collecting resource nodes (rope, herbs, gems). Your partner enters the Market and talks to NPCs, learning rumors and completing small quests.

Minute 45–50: You reunite at the Forest edge. You share your haul. Your partner shares intel: “The Merchant wants rope. She’ll trade a map fragment.” You have rope. Negotiation succeeds.

Minute 50–60: You use the map fragment to navigate to a sealed cave. At the entrance: a pressure-plate puzzle. Two plates, 20 meters apart. “Both must be held simultaneously for 10 seconds.”

You stand on plate 1. Your partner stands on plate 2. You coordinate: “On 3…” Both COMBINE (activate plates). Both COMMIT (hold). Cipher counts: “3… 2… 1…” Both press keys in sync. Door opens. Shared moment. Shared reward.

The emotional beat: You each contributed something the other couldn’t. Cooperation is required, not optional.

9.3 Complementary Roles

Scout archetype:

Fast movement, high dexterity.
Excels at wilderness navigation, avoidance, resource collection.
Combat advantage: evasion, ranged attacks.
Disadvantage: low persuasion, can’t negotiate with NPCs.

Negotiator archetype:

High charisma, persuasion.
Excels at NPC relationships, faction standing, information gathering.
Combat advantage: buffs, heals, status effects.
Disadvantage: slow movement, vulnerable to physical damage.

These are emergent roles, not enforced classes. But the design subtly rewards specialization.

9.4 Multiplayer Sync Protocol

How does the hybrid async/sync model actually work?

Sync Model Specification

Three synchronization contexts:

Exploration (ASYNC):
- Two linked operators can be in different zones simultaneously.
- Operator A is in the Forest. Operator B is in Market Square.
- Both are navigating the same procedural wilderness (seeded by shared cipher_seed).
- Each sees their own room description. No real-time sync required.
- Status bar shows: “[LINKED: OPERATOR_B (Market Square)]” so each knows where the other is.
Combat (SYNC-OPTIONAL):
- If Operator A encounters a monster while Operator B is elsewhere, combat triggers as solo combat.
- Screen shows: “COMBAT: Solo mode. Linked partner not present.” (Operator B sees notification: “OPERATOR_A is in combat with Shadow Drake.”)
- Combat proceeds normally. Operator A’s reputation changes are local (don’t affect Operator B until resync).
- Operator B can attempt to move toward Operator A’s location (via INFO to see zone, then navigate). If Operator B arrives mid-combat, sync engages.
- If both operators are in the same room at combat start: Sync combat triggers (turn-locked at 8s per turn, both taking turns alternately).
Puzzles (SYNC-REQUIRED):
- Pressure-plate puzzle: “Hold one plate, partner sprints through.”
- Dual-key lock: “Both keys inserted simultaneously.”
- These puzzles block solo completion. Screen shows: “LOCKED: Requires linked partner to proceed.”
- Before attempting, sync-check screen appears: “Sync check: OPERATOR_B ready? [CONFIRM]”
- Both operators must be present in the same room and must confirm. Then puzzle countdown starts.

Cable Disconnection and Error Recovery

Scenario 1: Cable loosens during exploration (async)

Status bar flashes: “[LINKED: OPERATOR_B ⚠ UNSTABLE]”
Latency detected. Communication remains, but degraded.
Operators can continue exploring independently (no functional loss).
Clear on-screen message: “Cable unstable. Connection may drop. Check your cable.”
If latency exceeds 500ms, sync operations (combat, puzzles) are blocked until cable is verified.

Scenario 2: Cable disconnects mid-puzzle (sync-required)

Puzzle attempt was in progress. Operator A holding plate, Operator B sprinting.
Cable dies. Operator B’s display freezes: “OPERATOR_A: CONNECTION LOST.”
Operator A’s display: “PARTNER DISCONNECTED. Puzzle auto-resets on your end.”
Clear error message: “Connection lost. Check cable and try again. [RETRY / CONTINUE SOLO / ABANDON]”
Options:
- RETRY: Resets puzzle from last checkpoint. Both operators attempt again.
- CONTINUE SOLO: Pressure-plate puzzle reverts to time-limit solo variant. Operator A holds plate, races timer (15s instead of 30s). Loses bonus reputation (5¤ instead of 25¤).
- ABANDON: Exit puzzle. Return to previous room.

Scenario 3: Operator disconnects via menu (intentional unlink)

Operator B presses SYS, selects “Disconnect.”
Screen shows: “Disconnect from OPERATOR_A? Unsaved progress may be lost. [CONFIRM]”
Both operators see: “LINK ENDED. Returning to solo play.”
Save data for both operators is immediately synced (push reputation, items, quest progress).
Operator A continues solo from current location.

Sync Verification and Handshake

Before synchronized challenges:

Screen shows: “Sync check: OPERATOR_B ready?”
Operator A presses CONFIRM.
The nOSh runtime checks latency: sends 20-byte ping, measures round-trip time.
If latency < 200ms: ”✓ Sync OK. Proceeding.”
If latency 200-500ms: ”✓ Sync OK (degraded). Proceeding.” (warning)
If latency > 500ms: ”✗ Sync UNSTABLE. Check cable. Retry? [YES / NO]“

Reputation and State Consistency

Solo combat (Operator A in combat, Operator B elsewhere):

Operator A’s reputation changes are LOCAL to Operator A’s cartridge.
Example: Operator A defeats a monster, gains +10 rep. Operator B doesn’t see rep change immediately.
On resync (when operators reunite): Reputation changes are NOT merged. Each operator retains their local changes.
Consequence: Two linked operators can have slightly different reputation scores (divergence), but this is acceptable (rewards independent play).

Linked combat (both operators in room, both in combat):

Reputation changes apply to BOTH operators equally.
Example: Defeat a boss together, both gain +50 rep.

Puzzles:

Puzzle completion rewards (reputation, items, unlocks) apply to both operators equally.
Example: Open the vault together, both get the rare item, both get +25 rep.

9.5 Solo Degradation

How much content is solo-playable?

Threshold is designed for 70% solo depth. All core gameplay loops work solo:

Exploration of handcrafted city and procedural wilderness
Quest completion (fetch, investigation, escort)
Combat encounters
NPC relationships

What requires multiplayer (30%):

Cross-operator puzzles (dual locks, pressure plates, synchronized challenges)
Multi-role quests (one operator scouts, the other negotiates — solo requires both roles, reducing efficiency)
Faction wars (high-rep quests that pit two factions against operators; linked partners can split allegiances, solo must choose one)

Solo consequence: A solo operator completes Threshold in 25-30 hours (full story arc). A linked pair completes in 20 hours with richer experience (shared discoveries, role specialization, emotional climaxes). Solo is satisfying but less memorable.

10. Audio Design

YM2149 Assignments

Voice 1 (Sonar Ambient & Depth Tone):

Base frequency encodes location type: Market (300Hz, bright), Temple (200Hz, spiritual), Wilderness (100Hz, vast), Combat (800Hz, alert).
Frequency modulates with threat (hostile NPC nearby: rises to 600Hz).
Special tones: Puzzle discovery (ascending arpeggio), quest unlock (chord stab), morally wrong choice (dissonant growl).

Voice 2 (Movement Feedback & Event Pulse):

Keypresses trigger soft tom hit (50ms, confirms input).
Room entry: rising glissando (welcoming tone for friendly zones, minor chord for dangerous zones).
NPC dialogue options: enumeration tone (1-second brief melody per option).
Checkpoint/milestone: triumphant arpeggio.

Voice 3 (Ambient & Threat Proximity):

Environmental mood (peaceful hum in Inn, eerie silence in Crypts, chanting in Temple).
Combat nearness: rising frequency as enemies approach (threat proximity encoding, same as DEPTHCHARGE).
Inventory changes: auditory texture shift (picking up Grappling Hook: metallic tink).

Ambient Soundscape

Market Square: merchants haggling (quiet chatter pad), coins clinking, distant blacksmith hammer. Temple: chanting monks, echoing footsteps, bell tolls. Wilderness: wind through trees, animal calls, distant water. Combat: clashing weapons, grunts, YM2149 threat tones.

Audio Narration Model for Screen-Off Play (New in Final Spec)

Design Principle

Every visual display has an audio-only equivalent. Narration uses Cipher voice (880 Hz, professional, diegetic) for consistency with the fiction. Not TTS—pre-recorded Cipher narration. This is essential work but enables true accessibility.

Audio Narration System

1. Room Descriptions (Narrated on Entry)

When you ENTER a room, Cipher narrates the description aloud:

Duration: ~3 seconds per room (medium rooms).
Pace: Clear, measured speech. Operators can follow while navigating.
Example: “Market Square. The heart of Threshold. Merchants hawk their wares from canvas stalls. You smell incense and hear the clank of a blacksmith’s hammer from a distance. Pigeons scatter as you approach. The fountain in the center is dry.”
Implementation: Every handcrafted room (35–45 rooms) has a pre-recorded narration. Procedural rooms use a template: “Forest clearing. Trees surround you. You see deer tracks in the moss. A stream runs to the north.”

2. NPC Dialogue Options (Enumerated as You Navigate)

When you CDR through dialogue options, Cipher reads them aloud:

Duration: ~1 second per option. Operator can pause and repeat (press INFO to re-enumerate).
Pace: List-like, numbered. “[1] Rest at the inn — costs 5 credits, restores health to maximum. [2] Hear the news about the distant lands. [3] Ask about the Widow. [4] Goodbye.”
Selection: Operator presses numpad 1-4 to choose. Cipher confirms: “You select option 1: Rest.”

3. Combat Status Updates

During combat, Cipher updates status every 3 seconds or on action change:

Example: “Your health: good, 42 of 50. Enemy health: moderate, 35 of 70. Enemy status: weakened stance. Your turn. 7 seconds remaining. Choose action: [1] Attack, [2] Defend, [3] Use item, [4] Flee, [5] Negotiate.”
Duration: ~2 seconds per update.
Feedback: Operator hears exact health values (numeric, not metaphorical) so they can make informed decisions.

4. Item Pickup Confirmation

When you COMBINE to pick up an item:

Tone-based feedback: Each item category has a unique YM2149 tone (identified above):
- Tools (rope, hook, key): High pitch (880 Hz), short pulse.
- Consumables (potion, bread): Low pitch (440 Hz), softer tone.
- Artifacts (rare items): Chord stab (A + E + C, triumphant).
Operator learns: Different tones = different item types. By ear, they know what they picked up.
Example: Operator picks up a rope. High-pitched ping. Operator immediately knows: “That’s a tool.”

5. Inventory Inspection via EXAMINE

When you EXAMINE an item in inventory:

Narration: “Rope. Tool. Condition: worn. Weight: 2 kilograms. Can be combined with: hook for grappling hook, or used alone for climbing.”
Duration: ~2 seconds per item.
Repeat: Operator can EXAMINE the same item again. Cipher repeats.
Screen-off gameplay: This is how you inspect inventory without a visual screen. No inventory UI; just audio narration.

6. Map Navigation (Compass Bearings)

Instead of visual ASCII map, Cipher provides audio navigation:

Narration: “You’re at Market Square, center of the city. North is Temple Quarter. East is Docks. South is Slums. West is Archive. You’ve visited 24 of 45 rooms in Threshold city core.”
Navigation aid: Operator builds a mental map. “North is the Temple. I should go north to reach the priestess.”
Procedural wilderness: “You’re at a forest clearing, coordinates E4. Northwest is a mountain pass. Southeast is a stream. South is a dungeon entrance.”

7. Partner Status (LINK Key Context)

When you press LINK to check your partner’s status:

Narration: “Linked partner: Alex. Location: Temple Quarter. Health: excellent, 48 of 50 HP. Inventory count: 4 items. Current quest: Retrieve the Crimson Ledger from the Vault.”
Duration: ~2 seconds.
Frequency: Can check anytime (press LINK). No cooldown.

8. Puzzle and Challenge Narration

When you encounter a puzzle or challenge:

Narration: “Pressure-plate puzzle. Two identical stone plates set into the ground 10 feet apart. Above them, an ornate brass door. The door’s lock glows faintly. You hear the hum of mechanical gears. To open the door, both plates must be pressed simultaneously.”
Duration: ~3 seconds.
Instruction: “To proceed, you must coordinate with your linked partner. Stand on one plate. Your partner stands on the other. Both press COMBINE on my signal. Ready? [CONFIRM]“

Implementation

Cartridge asset pipeline:

Pre-record Cipher narration for every distinct scenario (room, NPC option, combat status, puzzle, etc.).
Store audio as compressed 16-bit PCM at 22kHz (reduces file size while maintaining clarity).
Load on-demand (rooms load their narration when entered).
Falls back to silent if audio not available (graceful degradation).

Screen-off playability outcome:

Threshold is fully playable without a visual display.
Operators can navigate, talk to NPCs, engage in combat, solve puzzles, complete quests, and experience multiplayer cooperation, all by ear.
This matches ICE BREAKER’s screen-off accessibility.

11. Screen Layouts

Status Bar (Row 0, Firmware-Managed):

[LINKED: CIPHER ✓] REP: 320 CREDITS: 1,200¤ HEALTH: 40/50 QUESTS: 3

Main Room Display (Rows 1–23):

┌────────────────────────────────────────────────────────────────────────────┐
│ T H R E S H O L D                                                      [E3] │
├────────────────────────────────────────────────────────────────────────────┤
│                                                                             │
│  MARKET SQUARE                                                             │
│  ═══════════════════════════════════════════════════════════════════════   │
│  The heart of Threshold. Merchants hawk wares from canvas stalls.         │
│  You smell incense and hear the clank of a blacksmith's hammer from a    │
│  distance. Pigeons scatter as you approach. The fountain in the center   │
│  is dry.                                                                  │
│  ───────────────────────────────────────────────────────────────────────   │
│  EXITS:    N: TEMPLE QUARTER    E: DOCKS                                 │
│            S: SLUMS             W: ARCHIVE                               │
│                                                                             │
│  NPCS:     * QUEST-GIVER (mission available)                             │
│            + MERCHANT_ARLIN (trader)                                      │
│            = SCHOLAR_JAI (conversant)                                     │
│                                                                             │
│  ITEMS:    - copper coin        - torn scroll (quest objective!)         │
│            - wineskin                                                     │
│  ───────────────────────────────────────────────────────────────────────   │
│                                                                             │
│  ACTIONS:  [ENTER: drill in] [NEXT: sibling] [SCAN: look around]        │
│            [COMBINE: interact] [EXAMINE: inspect] [RETREAT: back]       │
│                                                                             │
├────────────────────────────────────────────────────────────────────────────┤
│ ▓░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░  │
└────────────────────────────────────────────────────────────────────────────┘

(Last row: progress/activity indicator bar)

NPC Dialogue Tree:

QUEST-GIVER
───────────────────────────────────────────
"The vault in the temple is locked. Two keys
guard it. I have rumors of where they're hidden.
Find them both, and I'll reward you generously."

OPTIONS:
  [1] Accept quest
  [2] Ask for details
  [3] Decline
  [4] Goodbye

Combat Screen:

┌────────────────────────────────────────────────────────────────────────────┐
│ COMBAT: SHADOW DRAKE                                      TURN 3 / 8 SEC  │
├────────────────────────────────────────────────────────────────────────────┤
│                                                                             │
│  YOUR HEALTH:    ▓▓▓▓▓▓▓▓░░ 40 / 50                                        │
│  ENEMY HEALTH:   ▓▓▓▓▓░░░░░ 35 / 70                                        │
│  ENEMY STATUS:   Weakened (2 turns remaining)                              │
│                                                                             │
│  ACTIONS:                                                                  │
│    [1] ATTACK with sword (70% hit chance, 8-12 damage)                   │
│    [2] DEFEND (next attack against you -40%)                             │
│    [3] USE ITEM - Healing potion (restore 20 HP)                         │
│    [4] FLEE (escape with reputation -2)                                  │
│    [5] NEGOTIATE (requires charisma, 50% success)                        │
│                                                                             │
│  Your choice: [1-5]                                                       │
│                                                                             │
└────────────────────────────────────────────────────────────────────────────┘

Inventory Screen (via SYS menu):

┌────────────────────────────────────────────────────────────────────────────┐
│ INVENTORY (6 / 10 slots)                                                   │
├────────────────────────────────────────────────────────────────────────────┤
│                                                                             │
│  TOOLS:                                                                    │
│    [1] Rope (worn, 2kg) — can COMBINE with hook                           │
│    [2] Lockpick set (good, 1kg) — for doors                              │
│    [3] Grappling hook (excellent, 1.5kg) — combines with rope             │
│                                                                             │
│  CONSUMABLES:                                                              │
│    [4] Healing potion (3x) — restore 20 HP each                           │
│    [5] Wineskin — restores stamina                                        │
│                                                                             │
│  ARTIFACTS:                                                                │
│    [6] Obsidian Shard (precious, 0.5kg) — quest objective                 │
│                                                                             │
│  ACTIONS:  [COMBINE: use item] [EXAMINE: inspect] [CLEAR: drop]         │
│                                                                             │
└────────────────────────────────────────────────────────────────────────────┘

Knowledge Menu (via SYS menu):

┌────────────────────────────────────────────────────────────────────────────┐
│ KNOWLEDGE ACQUIRED (12 facts)                                              │
├────────────────────────────────────────────────────────────────────────────┤
│                                                                             │
│  ✓ Cipher rotation pattern — numbers shift by 3 daily                      │
│  ✓ Temple priestess backstory — once a network operator herself            │
│  ✓ Merchant caravan route — takes the northern pass in winter             │
│  ✓ Guard post weakness — skeleton crew on new moons                        │
│  ✓ Archive librarian's fear — afraid of deep water                         │
│  [and 7 more...]                                                           │
│                                                                             │
│  SEARCH: ___________________                                               │
│                                                                             │
└────────────────────────────────────────────────────────────────────────────┘

12. Input System

Physical Layout: 31 keys + Numpad + SYS. See KN-86 Input System Architecture.

Function Key Bindings (80 Columns × 25 Rows Constraint):

All verbs are mapped to physical keys (CAR, CDR, CONS, etc.). On-screen labels use verb names (“[ENTER: drill in]”), not Lisp names.

Numpad Usage:

8/2/4/6: Cardinal direction selection (North/South/West/East) when prompted.
1/3/7/9: Diagonal directions (if supported by puzzle).
0/+/−/×/÷/.: Numeric input (password entry, damage rolls, cipher digits).
PAD_ENTER: Confirm numpad input.

Contextual Action Hints (Row 22–23):

Action hints change based on game state:

In inventory: “[COMBINE: merge items]”
In front of NPC: “[COMBINE: prepare offer to QUEST-GIVER]”
In dungeon with rope + wall hook: “[COMBINE: secure rope to hook]”
In combat: “[COMBINE: use item on self] or [COMBINE: use item on enemy]”

Hidden/Advanced Keys (Bound But Rarely Used):

ATOM: Predicate test (is this object a container?). Rarely needed in early play.
EQ: Compare identity (are these two items the same?). Used for quest verification.
LAMBDA/APPLY: Recording and replaying movement macros. Unlocked after 5+ hours.

13. Economy & Phase Chain Fit

Credits and Reputation

Credits (¤): Currency for NPC trades, equipment repairs, lodging. Earned by quest completion (5-100¤ per quest). Economy self-corrects via inflation scaling (expensive items cost more as credits accumulate, preventing softlock).

Universal Deck State Integration

Threshold correctly reads/writes:

credit_balance — quest payouts, equipment costs
reputation — quest completion, moral choices
cartridge_history bitfield — cleared dungeons, cross-module unlocks
cipher_seed — procedural wilderness seeding
knowledge_index — learned facts affecting puzzle difficulty

Cross-Module Mission Templates

Threshold registers mission templates with nOSh. Multi-phase campaigns (Threshold Phase 1 → Black Ledger Phase 2 → Threshold Phase 3) route through nOSh runtime managed phase_chain. The Cipher voice provides narrative continuity.

Bare Deck Terminal Support

Threshold is fully playable on a bare deck (no other cartridge loaded). However, if other cartridges are inserted, cross-module quests may unlock:

ICE BREAKER → Threshold: “Corporate malfeasance uncovered in Black Ledger; retrieve evidence from Threshold network contacts.”
Threshold → Black Ledger: “Seized financial records require audit. Enter Black Ledger cartridge to analyze.”

14. Cartridge Grammar Authoring

Cell Definition Sketches

All rooms, items, NPCs, and encounters are authored using the nOSh Cartridge Grammar (see docs/_archive/software/api-reference/grammars/cartridge-grammar-spec-v1.md). Below are representative examples:

Room Cell (Market Square)

CELL_DEFINE(MARKET_SQUARE,
  .cell_type = ROOM,
  .name = "Market Square",
  .description = "The heart of Threshold. Merchants hawk their wares from canvas stalls...",
  .exits = {
    { .direction = NORTH, .dest = TEMPLE_QUARTER },
    { .direction = SOUTH, .dest = SLUMS },
    { .direction = EAST, .dest = DOCKS },
    { .direction = WEST, .dest = ARCHIVE }
  },
  .npcs = { QUEST_GIVER, MERCHANT_ARLIN, SCHOLAR_JAI },
  .items = { COPPER_COIN, TORN_SCROLL, WINESKIN },
  .audio_id = "room_market_square_narration.pcm"
);

CELL_ON_CAR(MARKET_SQUARE, {
  // Player enters Market Square
  return DRILL_INTO(MARKET_SQUARE);
});

CELL_HANDLERS(MARKET_SQUARE, {
  .on_enter = market_square_on_enter,
  .on_examine = market_square_on_examine,
  .on_npc_interact = market_square_npc_interact
});

NPC Cell (Quest-Giver)

CELL_DEFINE(QUEST_GIVER,
  .cell_type = NPC,
  .name = "Quest-Giver",
  .description = "A weathered woman with sharp eyes. She trades in information.",
  .dialogue_tree = {
    .greeting = "The vault in the temple is locked. Two keys guard it...",
    .options = {
      { .text = "Accept quest", .callback = accept_vault_quest },
      { .text = "Ask for details", .callback = details_quest },
      { .text = "Decline", .callback = nil }
    }
  },
  .relationship = { .requires_rep = 0, .gain_on_complete = 25 }
);

CELL_ON_CONS(QUEST_GIVER, {
  // Player combines inventory with NPC (trade interaction)
  return trigger_npc_dialogue(QUEST_GIVER);
});

Item Cell (Rope)

CELL_DEFINE(ROPE,
  .cell_type = ITEM,
  .name = "Rope",
  .description = "Worn hemp rope. 2kg. Could be combined with a hook for climbing.",
  .type = TOOL,
  .weight = 2,
  .combinations = {
    { .with = HOOK, .result = GRAPPLING_HOOK }
  },
  .audio_id = "item_rope_pickup.pcm"  // High-pitch tone
);

Puzzle Cell (Dual-Lock Vault)

CELL_DEFINE(DUAL_LOCK_VAULT,
  .cell_type = PUZZLE,
  .name = "Sealed Vault",
  .description = "Two key slots, side-by-side. Above: an ornate brass door.",
  .puzzle_type = DUAL_KEY_LOCK,
  .required_items = { KEY_A, KEY_B },
  .sync_required = true,
  .on_solve = {
    .description = "The vault door swings open.",
    .reward = { OBSIDIAN_SHARD, .rep_gain = 25 }
  }
);

CELL_HANDLERS(DUAL_LOCK_VAULT, {
  .on_examine = dual_lock_examine,  // Explain the puzzle
  .on_eval_sync = dual_lock_attempt  // Execute when both operators press EVAL simultaneously
});

Cartridge Asset Pipeline

Rooms: 35–45 handcrafted rooms × 3 seconds narration = ~2 minutes of pre-recorded Cipher audio. NPCs: ~20 named NPCs × 5–10 dialogue options × 1 second per option = ~100–200 seconds. Puzzles: ~8–10 unique puzzle types × 3 seconds narration per = ~30 seconds. Total pre-recorded audio: ~5–7 minutes. Compressed PCM at 22kHz = ~3–4 MB cartridge footprint.

15. Save Data & Persistence

Global Shared World Persistence

Dungeon-Cleared Bitfield:

One bit per procedural dungeon (256-dungeon max per cartridge).
Once a dungeon is cleared (treasure looted, boss defeated), the bit is set.
All operators see the same cleared state.
Merged on unlink (union of both operators’ cleared states).

NPC Relationship State:

Per-NPC relationship flags (stranger, acquaintance, ally, enemy, romantic interest).
Persisted in cartridge save data (per-operator).
Not shared across operators.

Universal Deck State Snapshot:

credit_balance, reputation, knowledge_index, cartridge_history are synced when unlinking.
Each operator retains their own copy after unlinking.

Quest Progress:

Active quests, completed quests, quest stage tracked per-operator.
On unlink, quest state persists but is not synced between operators (each operator’s progress is independent).

16. Publisher & Branding

Publisher: Pacific Rim Dynamics

Pacific Rim Dynamics is a maritime-signal-processing collective treating the digital network as a shared commons. They position THRESHOLD as an exploratory experience, not a competitive game.

Narrative Voice:

Cipher: Professional, measured, diegetic (you’re really connected to a network).
NPCs: Diverse personalities, some helpful, some mercenary, some dangerous.
The world: Persistent, consequential, shared.

Visual Identity (Amber Monochrome):

Color: Amber (#E6A020) on black (#000000).
Font: Press Start 2P + CP437 box drawing (8×8 bitmap).
Aesthetic: Retro-futurism, 1980s hacker aesthetic meets fantasy adventure.

17. Accessibility

Sound-Only Play

Threshold is fully playable without a visual display, as specified in Section 10. Every element (rooms, NPCs, combat, puzzles, inventory) has an audio-only equivalent via pre-recorded Cipher narration.

Braille Keycap Support

Physical keycaps support braille dots (KN-86 Glyph Keycaps design). All keys are labeled with both glyph and braille, enabling blind operators to navigate by touch + audio.

Text-to-Speech Degradation

If pre-recorded Cipher narration unavailable, the cartridge falls back to TTS (text-to-speech) for room descriptions and dialogue options. Quality is degraded but playable.

18. Open Questions & Future Work

Major Design Decisions Under Scrutiny

Turn-based combat with 8-second timer — is this the right tempo?
- Risk: May feel too slow for action-oriented players; too fast for contemplative players.
- Playtesting focus: Record actual key-press timing from three operator personas. Adjust timer to 6s or 10s if consensus emerges.
Hybrid async/sync multiplayer model — is the complexity worth it?
- Risk: Operators become confused about when they need to synchronize. Latency edge cases (cable loosens mid-puzzle).
- Mitigation: Robust sync protocol with error recovery, sync-check pre-puzzles, and graceful degradation (single-operator variant).
- Playtesting focus: Run a full 2-hour linked session. Document all moments of confusion.
Procedural wilderness loses novelty after 10 hours.
- Risk: If biomes feel obviously procedural (copy-paste rooms, repetitive NPC names), the fiction breaks.
- Playtesting focus: Play 10 hours in wilderness. Assess: does the 100th procedural room feel like discovery or tedium?
Lisp key names (CAR/CDR/CONS) — can new players learn them despite on-screen verb hints?
- Risk: Even with verb hints, some players may feel frustrated by the jargon.
- Mitigation: On-screen hints use only verb names (“[ENTER]”, “[NEXT]”, “[COMBINE]”). Lisp jargon is hidden from the UI.
- Playtesting focus: Observe new players in the first 15 minutes. Do they ask about key names? Do they feel confused?
Knowledge system is invisible — will players notice they’re learning?
- Risk: Players may not feel “powerful.” Progression may be opaque.
- Mitigation: Knowledge system now has explicit feedback (Cipher voice, SYS menu integration, visible mechanics).
- Playtesting focus: Ask testers: “Do you feel yourself improving?” Track their understanding of knowledge mechanics.

Risk Inventory

Risk	Probability	Impact	Mitigation
Multiplayer latency breaks puzzles	Medium	High	Extensive cable stress-testing. Robust error recovery (retry, degrade to solo variant).
Solo mode feels incomplete	Medium	Medium	Design so solo has 70% of multiplayer depth. Ship single-player campaign as full product.
Procedural wilderness becomes tedious	Medium	Medium	Vary biome structure. Seed biomes with handcrafted encounter tables.
Lisp jargon confuses new players	Low (mitigated by verb hints)	Medium	On-screen hints use verbs only. Lisp names hidden. Tutorial teaches via context.
Sync protocol is too complex	Medium-High	High	Playtesting with actual linked pairs. Consider simplifying if confusion emerges.
Knowledge system invisible	Low (mitigated)	Medium	Explicit feedback, SYS menu integration, Cipher narration.
Audio narration is costly	Medium	Low	Pre-recorded Cipher voice, not TTS. Phased implementation (launch with room narrations, add dialog/combat narrations in patch).
Onboarding is still confusing	Low (with tutorial)	Medium	Run first-time player sessions. Iterate on tutorial sequence.
World persistence creates save-data bloat	Low	Low	Efficient bitfield packing. Procedural biomes don’t store per-room state.

Playtesting Focal Points

New in Final Spec (building on Round 1 and 2):

First 30 minutes with a new coop pair: Does the onboarding arc land? Is the early coop moment (dual-lock puzzle) emotionally resonant?
Screen-off play: Can operators navigate, talk to NPCs, and complete quests without a visual display?
Verb disambiguation: Do operators naturally understand which COMBINE operation is active, or do they stumble?
Multiplayer sync: Run a 2-hour linked session with intentional cable stress (loosen, briefly disconnect, etc.). How do operators handle edge cases? Is error recovery clear?
Knowledge system: Do operators notice when they learn something? Do they review the knowledge menu? Does knowledge feedback feel rewarding?
Lisp key names: Do operators ask “why is it called CAR?” or do the verb hints abstract it away?
Procedure wilderness after 10 hours: Does the 200th procedural room still feel like exploration, or does it feel like tedium?
EXAMINE key binding: Is F10 accessible and intuitive, or does it conflict with screen-capture muscle memory?

19. Changelog — Round 1 → Round 2 → Final

Round 1 → Round 2 Additions

Procedural Wilderness Persistence: Specified GLOBAL dungeon-cleared state, shared across operators.
Multiplayer Sync Protocol: Detailed three contexts (async exploration, sync-optional combat, sync-required puzzles), cable disconnection scenarios, sync-check handshakes.
Knowledge System: Made explicit with Cipher feedback, SYS menu integration, mechanical effects.
Item Combination Reversibility: CONS consumes originals, creates new item. Decombination possible with Scissors.
Early Coop Hook: Dual-lock puzzle at minute 15–20 forces cooperation and establishes multiplayer as essential.
Context-Aware Verb Hints: UI disambiguates CONS via on-screen hints (“[COMBINE: merge items]” vs. “[COMBINE: prepare offer]”).
EXAMINE Verb: New verb for deep object inspection, separating from APPLY’s LAMBDA execution semantics.
Audio Narration System: Comprehensive specification for screen-off play (room narrations, NPC dialogue, combat, inventory, map navigation).
Onboarding Arc: Scripted first 30 minutes with diegetic tutorial NPC (KEEPER).
Publisher Change: Edgeware → Pacific Rim Dynamics (better thematic fit).

Round 2 → Final Additions

EXAMINE Key Binding: Locked to F10 (design decision made).
Section Depth: Expanded all sections with explicit examples, screen mockups, cartridge grammar sketches, audio design detail.
Collision Audit Table: Cross-module verb grammar verification (all verbs coherent with Lisp Paradigm).
World Architecture Tree: Explicit room hierarchy diagram (THRESHOLD_CITY → hubs → interiors → private rooms).
Sync Protocol Detail: Comprehensive error recovery, reputation consistency rules, handshake specifications.
Screen Layouts: Full ASCII mockups of main room display, combat, inventory, knowledge menu.
Asset Pipeline: Specific cartridge footprint estimates (3–4 MB for pre-recorded audio).
Accessibility: Braille keycap support, TTS fallback, sound-only playability.
Risk Inventory: Quantified risks with probabilities and mitigations.
Playtesting Focal Points: Eight specific areas for Round 3 validation.

What Each Round Added

Round 1 (Playtest Foundation): Core design, world architecture, multiplayer promise.

Round 2 (Playtest Feedback Integration): Specificity across all systems, audio narration, early coop hook, sync protocol, knowledge system visibility, verb disambiguation.

Final (Engineering Ready): Complete detail, exact key bindings, cartridge grammar examples, screen mockups, comprehensive risk analysis, explicit playtesting focus areas.

20. Design Summary

THRESHOLD is a choice-based MUD redesigned for the Lisp keypad interface and optimized for multiplayer-first party play. Two operators with complementary roles (scout + negotiator) navigate a handcrafted city core plus infinite procedural wilderness, solving puzzles, managing relationships with NPCs, and completing multi-stage quests.

Three Biggest Design Choices

Lisp list navigation as the entire interaction model. CAR/CDR/CONS are genuine list operations. Rooms are nested lists. Mastery feels like learning the world’s structure, not memorizing shortcuts. On-screen hints use plain-English verbs, teaching domain meaning without jargon.
Hybrid async/sync multiplayer with early coop hook (minute 20). 70% of content is solo-playable. 30% requires cooperation (cross-operator puzzles, synchronized quests). By minute 20, new operators have experienced “we did something together that neither of us could do alone,” establishing multiplayer as essential.
World persistence and shared fiction. Cleared dungeons are global. NPCs remember you. The network feels real and alive, not randomly generated per session. Your choices matter and persist globally.

Three Biggest Risks

Latency on the TRRS serial link breaks synchronized moments. If cable is loose or connection noisy, puzzles fail mysteriously. Mitigation: robust sync protocol with error recovery, sync-check pre-puzzles, and graceful degradation (single-operator variant).
Procedural wilderness loses novelty after 10 hours. Biome generation must vary enough that the 100th forest room doesn’t feel identical to the first. Needs handcrafted encounter tables + procedural positioning.
Multiplayer coordination overhead creates confusing moments. Two operators at different time scales may create frustration. Mitigation: partner status visibility, shared map access, message system, explicit sync indicators.

Appendix: Reference Material

Required Reading (Linked):

/sessions/wonderful-tender-faraday/mnt/kinoshita/CLAUDE.md — Canonical Hardware Specification
/sessions/wonderful-tender-faraday/mnt/kinoshita/docs/software/runtime/orchestration.md — Software model, economy, phase chain
/sessions/wonderful-tender-faraday/mnt/kinoshita/docs/_archive/software/api-reference/grammars/cartridge-grammar-spec-v1.md — C authoring framework
/sessions/wonderful-tender-faraday/mnt/kinoshita/docs/software/cartridges/authoring/lisp-paradigm.md — Verb semantics across modules
/sessions/wonderful-tender-faraday/mnt/kinoshita/docs/software/runtime/input-dispatch.md — 31-key layout and event model

Sibling Specs (Format Reference):

KN-86-Depthcharge-Gameplay-Spec.md (1,915 lines)
KN-86-NeonGrid-Gameplay-Spec.md (1,610 lines)
KN-86-BlackLedger-Gameplay-Spec.md (1,847 lines)

Design Iteration History:

Round 1: /sessions/wonderful-tender-faraday/mnt/kinoshita/docs/gameplay-specs/drafts/MUD-Design-Round1.md (archived)
Round 2: /sessions/wonderful-tender-faraday/mnt/kinoshita/docs/gameplay-specs/drafts/MUD-Design-Round2.md
Playtest Reports: playtest-round2-corwin.md, playtest-round2-vex.md, playtest-round2-mae.md

Document Status: Final Spec. Engineering-Ready.

Next Phase: Specification review (design audit), followed by implementation via C-based cartridge authoring. Pre-recorded Cipher audio pipeline in parallel.

Absolute path of this document: /sessions/wonderful-tender-faraday/mnt/kinoshita/docs/software/cartridges/modules/threshold.md

Version 1.0 — April 21, 2026

CIPHER-LINE Contributions

Threshold’s voice: the deck as sympathetic chronicler of the expedition. Peripheral ambience while the operator reads main-grid room text. Fragments observe mood, remember past rooms, drift through atmospheric recall.

Vocabulary Pools

(:subject       "room" "door" "figure" "lamp" "dust"
                "shadow" "step" "voice" "stranger" "party")
(:object        "threshold" "corridor" "path" "lock" "seal"
                "mark")
(:location      "ward" "hall" "chamber" "gate" "stair")
(:verb-present  "holds" "watches" "listens" "creaks" "flickers"
                "shifts")
(:verb-past-participle "crossed" "opened" "sealed" "lost" "found"
                       "remembered")
(:memory-keyword "room" "lamp" "stranger" "door" "gate")
(:affect-word   "dim" "bright" "cold" "warm" "still" "watched")

Production Fragments

(:mode-observe
  (3 (:subject) ". " (:affect-word) ".")
  (2 "the " (:location) " " (:verb-present) ".")
  (1 "threshold."))

(:mode-annotate
  (3 (:affect-word) " here.")
  (1 "someone left this."))

(:mode-reflect
  (3 "same lamp. " (:memory-fragment))
  (3 "this gate. " (:memory-fragment))
  (2 (:memory-fragment) ". and before."))

(:mode-drift
  (3 "the stranger at the inn.")
  (2 "a door that wouldn't open.")
  (1 "a hall nobody crossed twice."))

:event-types
  ((:type :room-entered     :affect (:routine))
   (:type :npc-met          :affect (:routine))
   (:type :quest-advanced   :affect (:significant))
   (:type :party-synced     :affect (:significant))
   (:type :death            :affect (:tense :anomalous)))

Mode-Weight Biases

Beat	`observe`	`annotate`	`reflect`	`drift`	`silent`
`:bare-deck` (solo Threshold)	—	—	+0.15	+0.20	—
`:active-hack` (exploration)	—	+0.05	+0.10	+0.10	+0.05
`:high-tense` (combat)	—	—	—	—	+0.20
`:cart-swap-lull`	—	—	—	+0.15	—

Rationale. Threshold’s main-grid is dense with room/NPC/quest text. CIPHER-LINE stays peripheral — reflect and drift dominate, silence-heavy during combat. The cart is explicitly designed to not compete with its own main-grid content.

Style Deltas

((:bare-deck     (:temporal-blur +32))
 (:active-hack   (:temporal-blur +40 :terseness +16))
 (:high-tense    (:terseness +56)))

Threshold tolerates more temporal blur than any other cart — the genre invites drift between “here” and “remember.”

Multiplayer Note

CIPHER-LINE is deck-local. In a 2-operator party session, each operator sees independent Cipher output on their own CIPHER-LINE. Coherence stacks are not shared across the LINK protocol; each deck’s voice remembers its own journey. This is correct — the Cipher voice is an internal subsystem, not a multiplayer chat channel.

Structurally Important Moments Preserved on CIPHER-LINE

Beat	Intent	CIPHER-LINE fragment(s)
New room entered	(ambient)	`dim here.` or `(silent)`
NPC met for the first time	”A stranger offers a deal.”	`stranger. watching.`
Quest advanced	”The map opens. New path available.”	`path. open.`
Party synced	”Your partner holds the other key.”	`two keys. one lock.`
Combat	(tense)	`(silent)` as PSG combat pattern rises
Death	”You have fallen.”	`fell.` (anomalous; sticks in coherence stack for many ticks afterward)

nEmacs Contributions

Per ADR-0016 (nEmacs + REPL + Input Model), each cart declares what its scripted-mission surface looks like — grammar fragments contributed to the predictive palette, domain vocabulary that earns the +5 ranking boost (ADR-0016 §7), whether it uses prompt-text for raw text entry (§8), and whether any of its keys bind :double-tap or :long-press events (§9). Threshold is the cross-module MUD — party coordination, quest chains, exploration scripting — and its nEmacs contribution is notable because it’s the one launch cart whose scripting reaches across other carts (scripted-mission forms that reference NPC / item / location records from linked cartridges).

Scripted Missions?

Yes — exploration and party-coordination scripting. Threshold’s Lisp list-structure-as-world makes it unusually natural for scripted missions. Rep-8+ operators unlock Cartographer and Quartermaster bounties that expressly reward scripted helpers: auto-map builders, inventory-sort routines, party-status monitors. For the multiplayer path, operators can author shared quest triggers that fire cooperatively across two decks via the LINK protocol. Scripted missions remain optional on the critical path (ADR-0002) — a low-rep operator plays Threshold entirely through room-by-room primitive navigation. High-rep operators weave scripted helpers around their expeditions.

Typical scripted-mission shapes:

(auto-map room-tree) — builds a cartographic graph of visited rooms.
(on-npc-met name (if (reputation-above 5) (greet) (avoid))) — reactive.
(inventory-sort :by :weight) — utility helper.
(party-status) — peer-deck status read.
(quest-beat-hook quest-id beat-id &body handler) — scripted party-sync.

Cart Grammar Fragments

Contributed via (emacs-extend-grammar ...) at cart-load. This is the second-heaviest grammar contribution after Relay, reflecting Threshold’s MUD scope:

(emacs-extend-grammar
  ;; World navigation
  (room               (&optional id))            ; current room if no id
  (exits              (&optional room-id))
  (room-desc          (&optional room-id))
  (look               (&optional :direction))
  (enter              (direction-or-door))
  (next               (direction))               ; adjacent-room traversal
  (back)
  ;; NPCs and items
  (npcs-here)
  (npc                (name))
  (talk-to            (npc-name template))
  (items-here)
  (item               (id))
  (inventory)
  (take               (item))
  (drop               (item))
  (combine            (a b))
  (equip              (item))
  ;; Quest primitives
  (quests)
  (quest              (id))
  (quest-advance      (id beat-id))
  (quest-beat-hook    (id beat-id &body handler))
  ;; Party / LINK
  (party)
  (peer-operator)
  (peer-location)
  (link-status)
  (sync-with-peer     (ritual))
  ;; Combat
  (combat-state)
  (enemies-here)
  (attack              (target &key :weapon))
  (defend)
  (flee)
  ;; World introspection
  (auto-map           (&key :depth))
  (reputation-with    (faction-or-npc))
  (on-room-entered    (&body handler))
  (on-npc-met         (&body handler))
  (on-party-synced    (&body handler)))

Vocabulary Contribution

Via (emacs-extend-vocabulary ...). MUD-adventure / party / quest terms:

(emacs-extend-vocabulary
  "room" "hall" "chamber" "gate" "door" "threshold"
  "stair" "corridor" "bridge" "ward" "tower"
  "north" "south" "east" "west" "up" "down"
  "npc" "stranger" "merchant" "guard" "scholar"
  "item" "key" "lamp" "seal" "mark" "scroll"
  "inventory" "equipped" "held" "stored"
  "quest" "beat" "chapter" "chain" "epilogue"
  "party" "peer" "link" "sync" "rendezvous"
  "combat" "attack" "defend" "flee" "parry"
  "reputation" "trust" "faction" "standing"
  "crossed" "opened" "sealed" "lost" "found"
  "explore" "map" "charted" "unexplored")

`prompt-text` FFI Usage

Maybe — NPC dialogue and party messaging. The task brief lists Threshold as “Maybe”; the cart has two plausible call sites, but both are diegetic-tight enough that they might be replaced with menu selections in implementation:

Call site	Purpose	Typical length
NPC dialogue input	Operator types a reply to an NPC whose conversation branches are unscripted enough to need it	5–60 chars
Party message	Send a free-text message to the party peer over LINK during exploration	10–200 chars

Both are candidates for ADR-0016 §8’s “short modal” use case. If playtest shows NPC dialogue feels better with curated menu options, the call is dropped; if party messaging is frequent, it may graduate to Relay-style centrality (triggering the §6 autocomplete revisit noted in ADR-0016 §“What we’ll revisit”). Ships with prompt-text declared; usage volume is a v1.x tuning knob.

Double-Tap and Long-Press Bindings

Threshold opts into ADR-0016 §9 on keys that benefit from drill-down in a text-heavy adventure:

Key	`:tap`	`:double-tap`	`:long-press`
`INFO`	`look` — short room description	`look-deep` — full description with hidden detail	`show-map-local` — render mini-map of nearby rooms
`CAR`	`enter` — enter the focused exit / door	`enter-and-look` — enter then immediately describe	—
`CDR`	`next` — adjacent-room traverse	—	—
`CONS`	`combine-items`	—	`show-combination-hints` — reveal known recipes
`EVAL`	`commit-action` (attack / talk / use)	—	`commit-carefully` — with confirmation (for destructive actions)
`QUOTE`	`mark-room`	`bookmark-room`	—

Row 24 renders: INFO:LOOK INFO²:DEEP INFO…:MAP CAR:ENTER CAR²:ENTER+LOOK CONS:COMBO EVAL:ACT QUOTE:MARK.

Context-Polymorphic Key Semantics (Cart Gameplay)

Threshold’s cart has multiple cursor contexts reflecting its MUD scope: exploration (navigating rooms), dialogue (talking to NPC), inventory (managing items), combat (8-second turn cycle), party (peer-sync view):

Key	Exploration	Dialogue	Inventory	Combat	Party
`INFO`	look	show-npc-metadata	show-item-details	show-combat-state	show-peer-status
`CAR`	enter	descend-topic	drill-into-item	target-enemy	drill-peer-action
`CDR`	next-exit	next-topic	next-item	next-enemy	next-peer-event
`CONS`	combine-room-features	add-topic-to-quest	combine-items	bind-action-to-hotkey	initiate-sync
`EVAL`	execute-action	reply (via prompt-text or menu)	use-item	commit-attack	commit-sync-ritual
`QUOTE`	mark-room	flag-npc	flag-item	flag-enemy	flag-beat
`BACK`	return-to-last-room	exit-dialogue	exit-inventory	flee	exit-party-view
Numpad	exit selection	reply-option select	item-slot select	target select	peer event select

When the operator opens nEmacs to author an expedition helper, dispatch yields to :nemacs-nav per ADR-0016 §3 — standard editor dispatch. Threshold pauses all scripted timers (NPC patrols, quest clocks) while nEmacs is open; the world resumes on return.

Party-Mode and Scripted Mission Coordination

For multiplayer play, scripted missions can hook into peer events. A quest beat hook authored on one deck fires when the peer’s deck sends the matching sync event over LINK. Both decks must have the quest’s cart grammar loaded (typical case — both operators carry Threshold during a shared expedition). The shared hook surface is deliberately small — sync ritual keys, party-status queries, and the on-party-synced binder — to keep multiplayer scripting legible.

THRESHOLD — Gameplay Specification

Mission Contributions

Design Philosophy

1. Executive Summary

2. Diegetic Premise & Fiction

3. Core Fantasy & Player Promise

4. Lisp Verb Mapping & Grammar

Analysis Against Existing Paradigm

Final Verb Map for Threshold

Collision Analysis & Auditing

5. Capability Model Integration

Universal Deck State Integration

Mission Board Integration

Phase Chain Handling

World Persistence Model

6. World Architecture

Overview

The Handcrafted Core: Threshold City

Key Locations

Handcrafted Critical Path

Procedural Wilderness

7. Core Loop

15-Minute Session

60-Minute Session

2-Hour Session (Multiplayer)

Onboarding and Early Coop Hook (New in Final Spec)

Minute 0–5: Boot, Link, Orientation

Minute 5–10: Tutorial with Keeper NPC

Minute 10–15: First Independent Exploration (Solo in Different Zones)

Minute 15–20: FIRST COOP MOMENT — Dual-Lock Puzzle

Minute 20–30: Follow-Up Momentum

8. Mechanics

8.1 Movement & Navigation

8.2 Inventory & Item System

8.3 NPC Dialog

8.4 Combat

8.5 Quests

8.6 Progression System

9. Multiplayer-First Party Play

9.1 The Differentiator

9.2 What Linked Play Actually Feels Like

9.3 Complementary Roles

9.4 Multiplayer Sync Protocol

Sync Model Specification

Cable Disconnection and Error Recovery

Sync Verification and Handshake

Reputation and State Consistency

9.5 Solo Degradation

10. Audio Design

YM2149 Assignments

Ambient Soundscape

Audio Narration Model for Screen-Off Play (New in Final Spec)

Audio Narration System

Implementation

11. Screen Layouts

12. Input System

13. Economy & Phase Chain Fit

Credits and Reputation

Universal Deck State Integration

Cross-Module Mission Templates

Bare Deck Terminal Support

14. Cartridge Grammar Authoring

Cell Definition Sketches

Room Cell (Market Square)

NPC Cell (Quest-Giver)

Item Cell (Rope)

Puzzle Cell (Dual-Lock Vault)

Cartridge Asset Pipeline

15. Save Data & Persistence

Global Shared World Persistence

16. Publisher & Branding

17. Accessibility

Sound-Only Play

Braille Keycap Support

Text-to-Speech Degradation

18. Open Questions & Future Work

Major Design Decisions Under Scrutiny

Risk Inventory

Playtesting Focal Points

19. Changelog — Round 1 → Round 2 → Final

`prompt-text` FFI Usage