Salt & Steel: Full System Interconnection Map

Topology document defining the complete system architecture for Salt & Steel — a pirate-themed ARPG built on GURPS mechanical foundations with Path of Exile's depth and ethical free-to-play business model.

1. System Inventory

Salt & Steel is composed of more than 45 discrete, nameable systems that interact across five architectural domains: character, world & content, economy, naval, and infrastructure. The complete inventory:

Character Domain (GURPS-Adapted)

• Attribute System — Four primary attributes from GURPS (ST, DX, IQ, HT) adapted for real-time play; governs derived stats (HP, FP, Will, Perception, Basic Speed, Basic Move)
• Secondary Characteristics — Derived values calculated from primary attributes: Hit Points (from ST), Fatigue Points (from HT), Will (from IQ), Perception (from IQ), Basic Speed (from DX+HT), Basic Move (from Basic Speed), Dodge (from Basic Speed)
• Skill Atlas — Vast point-buy progression map replacing the traditional passive tree; thematic regions (Sea Dog, Corsair, Alchemist, Duelist, Navigator, etc.) where spending character points unlocks skills, advantages, attribute bonuses, and technique specializations
• Advantage/Disadvantage System — Build-defining traits adapted from GURPS; Advantages (Combat Reflexes, High Pain Threshold, Ambidexterity, Danger Sense, Hard to Kill, Luck) and Disadvantages (Code of Honor, Overconfidence, Bad Temper, One Eye, Greed) that create unique character identities with mechanical teeth
• Active Skill System — Learned abilities (not socketed gems) organized into Combat, Social, Nautical, Survival, and Arcane trees; skills have GURPS-style defaults and prerequisites; deep combinatorial system through Technique specializations that modify base skills
• Combat Stance System — Real-time adaptation of GURPS maneuvers: All-Out Attack (Determined, Strong, Double), All-Out Defense (Dodge, Parry, Block), Defensive Attack, Move and Attack, Committed Attack, Wait/Evaluate; each stance modifies offense/defense tradeoffs per combat tick
• Active Defense System — Three active defense types from GURPS (Dodge, Parry, Block) implemented as real-time mechanics; Dodge includes a dodge-roll with i-frames; Parry uses equipped weapon skill; Block uses shield skill; each defense has a calculated target number on 3d6
• Fatigue System — GURPS Fatigue Points (FP) replacing traditional mana; all abilities cost FP; FP recovers through rest, food, drink, and specific advantages; exhaustion penalties cascade at low FP (reduced attributes, collapse at 0, potential death at negative FP)
• Wound/Injury System — GURPS hit location and wound severity adapted; major wounds cause shock penalties; crippling injuries affect limb function; bleeding as persistent damage; recovery through rest, medicine skill, and healing items
• Crew/Companion System — Recruited NPCs with their own attribute scores, skills, advantages, and equipment; crew members serve roles (Gunner, Surgeon, Bosun, Lookout, Cook); provide passive bonuses and active abilities in both land and naval combat
• Character Origin System — Starting backgrounds (Privateer, Buccaneer, Merchant Captain, Navy Deserter, Witch Doctor, Scholar) that determine starting attribute distributions, initial skill points, and Skill Atlas starting position

World & Content Domain

• Campaign Structure — 15-chapter narrative spanning Caribbean-inspired archipelago, West African coast, Mediterranean waters, and mythic seas; each chapter introduces new mechanics, factions, and geographic regions
• Nautical Chart — Endgame atlas equivalent; an expanding sea chart of explorable waters, islands, reefs, and deep ocean zones that grows through discovery, cartography, and geographic expansions; each region has unique monster ecology, treasure profiles, and environmental hazards
• Island/Dungeon Generation — Procedural generation of explorable islands, sea caves, ruins, shipwrecks, underwater grottos, and fortifications; modular tileset composition with hand-crafted landmark rooms and boss arenas
• Naval Combat System — Ship-to-ship battles as a distinct combat layer with broadside volleys, boarding actions, ramming, pursuit maneuvers, and weather effects; operates on different mechanical scale than personal combat
• Port Towns and Havens — Persistent social hubs with vendors, taverns, harbormasters, faction representatives, black markets, and crafting stations; separate instances per server region
• Voyage System — Seasonal content equivalent; themed multi-week expeditions (e.g., "The Kraken's Wake," "Curse of the Sargasso," "El Dorado") that add temporary mechanics, exclusive encounters, themed loot, and a seasonal leaderboard without full economy resets
• Boss Encounters — Legendary pirates, sea monsters (Kraken, Leviathan, Charybdis), cursed captains, colonial admirals, and mythic beings; multi-phase encounters with naval and personal combat phases
• Weather and Sea State System — Dynamic weather affecting visibility, navigation, combat accuracy, and ship handling; storms, fog, doldrums, monsoons, waterspouts; weather patterns tied to regions and seasons
• Treasure System — Treasure maps, buried treasure, sunken ship salvage, artifact hunting, and legendary hoard quests; treasure quality scaled by map tier and region danger level
• Exploration/Discovery System — Charting unknown waters, discovering hidden coves, mapping reefs, identifying currents; feeds into the Nautical Chart progression and provides cartography-based rewards
• Faction System — Multiple competing factions (Pirate Brotherhood, Royal Navy, Trading Companies, Smuggler Guilds, Witch Doctor Circles, Ancient Orders) with reputation tracks, exclusive rewards, and inter-faction conflicts
• World Event System — Dynamic events: fleet engagements, port sieges, treasure flotillas, sea monster migrations, ghost ship sightings; events scale with player count and world state
• Environmental Hazard System — Reefs, whirlpools, volcanic vents, cursed waters, sea monster territories, naval blockades; hazards modify both navigation and combat encounters

Economy Domain

• Currency System — Functional currencies with crafting utility (like PoE orbs but pirate-themed): Doubloons (general trade), Pieces of Eight (high-value transactions), Trade Goods (region-specific commodities), Salvage Tokens (crafting material), Letters of Marque (endgame currency); each currency type has a crafting function
• Crafting System — Multiple crafting disciplines: Blacksmithing (weapons/armor), Sailmaking (ship sails), Carpentry (ship hulls), Alchemy (potions/poisons/enchantments), Gunsmithing (firearms/cannons), Cartography (treasure maps/navigation charts), Scrimshaw (bone/ivory charms with magical properties)
• Modifier System — Item affix architecture: prefix/suffix system with pirate-themed modifier pools; tiered affixes gated by item level; influence types (Cursed, Blessed, Voodoo, Masterwork) that unlock additional modifier pools
• Trade System — Port marketplace with automated commodity trading; black market for restricted/stolen goods; smuggling networks for cross-region arbitrage; player-to-player direct trade for high-value items
• Loot Generation — Server-side RNG drop system; treasure chests, monster drops, salvage from wrecks, plunder from defeated ships; item level gating, drop weighting by region and encounter tier
• Loot Filter System — Scriptable display rules for dropped items; community-maintained filter templates; filters for both personal loot and ship salvage
• Vendor/Fence System — NPC merchants with rotating inventories; Fences for stolen goods; Alchemists for potion ingredients; deterministic recipe system (combine specific items for guaranteed outputs)

Naval Domain

• Ship Types and Classes — Progressive ship tiers: Rowboat, Pinnace, Sloop, Brigantine, Frigate, Galleon, Man-o'-War, Flagship; each class has distinct stat profiles (speed, hull strength, cannon capacity, crew capacity, cargo hold)
• Ship Customization — Modular ship components: Hull (armor/speed tradeoff), Sails (speed/maneuverability), Cannons (port/starboard/bow/stern slots), Figurehead (passive bonuses), Crew Quarters (crew capacity/morale), Cargo Hold (storage capacity), Ram (boarding/ramming bonuses), Special Equipment (diving bell, telescope, astrolabe)
• Ship Combat System — Broadside volleys with cannon types (chain shot, grape shot, bar shot, cannonball), boarding actions (triggers personal combat on enemy deck), ramming attacks, pursuit/escape mechanics, wind advantage positioning
• Ship Damage Model — Component-based damage: hull breaches (flooding), mast damage (speed reduction), sail damage (maneuverability loss), cannon destruction (firepower reduction), crew casualties, fire spread; damage repaired via crew actions, port services, or emergency materials
• Fleet Management — Endgame system: players command multiple ships; assign NPC captains; fleet formations for large-scale encounters; fleet-vs-fleet battles; convoy protection missions
• Port/Harbor System — Docking at ports for repairs, resupply, crew recruitment, trade, and quest access; port reputation affects available services and prices; hostile ports require smuggling or combat
• Sea Navigation System — Wind direction and strength affecting sail-powered movement; ocean currents as movement modifiers; compass and sextant for positioning; fog of war on unexplored chart regions; landmark navigation
• Seamless Transition System — Smooth transitions between ship deck (naval combat), below deck (ship interior), landing boat (shore approach), and island/dungeon exploration without loading screens where possible

Infrastructure Domain

• Client Architecture — Custom engine with DX12/Vulkan rendering; deferred renderer with PBR materials; dynamic ocean rendering with wave simulation; seamless zoom between ship view and personal view; particle system for cannon fire, weather, and skill effects
• Server Architecture — Server-authoritative design; dual instance types (sea instances for naval play, land instances for exploration); Account Authority service; separate services for trade, social, voyage tracking
• Networking Model — Server-authoritative with lockstep and predictive modes; TCP with delta updates; area-of-interest filtering for both naval (ship-scale) and personal (character-scale) contexts; seamless sea-to-land transition protocol
• Authentication and Session Management — OAuth 2.1 authentication; session persistence across sea/land transitions; account-bound character and ship data; cross-platform account support
• Instance Management — Sea zone instances (large, shared, persistent within session), land instances (private/party, generated on entry), port town instances (shared social hubs), boss arena instances (private/party, despawned on completion)
• Security Systems — Server authority as primary anti-cheat; all combat resolution, loot generation, and economy transactions server-validated; area-of-interest filtering prevents information leakage; ban waves for RMT and exploits
• Monetization Systems — Cosmetic-only MTX: ship skins, sail designs, figureheads, weapon effects, character outfits, pet parrots/monkeys; convenience: expanded cargo hold tabs, crew management UI upgrades; supporter packs with exclusive cosmetics; zero pay-to-win
• Social Systems — Crews (guild equivalent with shared ship, crew roster, treasury); party play (up to 6 for land, fleet coordination for sea); PvP (naval duels, port arena, open-sea PvP zones); chat, emotes, signal flags; community tools API for build planners and trade sites
• Visual/Audio Pipeline — Dynamic ocean renderer; volumetric fog and weather; adaptive shanty/ambient music system; 3D positional audio for naval combat (cannon impacts, wind, wave crashes, creaking wood); day/night cycle with lighting changes
• UI/UX Layer — HUD with health/FP bars, compass, wind indicator, minimap; ship management overlay; Skill Atlas interface (zoomable cartographic map); inventory/cargo management; Nautical Chart interface; crew roster management

2. Interconnection Matrix

Attribute System (ST/DX/IQ/HT)

Skill Atlas

Active Skill System

Advantage/Disadvantage System

Combat Stance System

Active Defense System (Dodge/Parry/Block)

Fatigue System (FP)

Crew/Companion System

Damage Calculation Pipeline (GURPS 3d6 Adapted)

Currency System

Nautical Chart (Endgame Atlas)

Naval Combat System

Crafting System

Trade System

Voyage System (Seasonal Content)

Ship Types and Classes

Weather and Sea State

Faction/Reputation System

3. Mermaid Diagrams

Diagram 1: High-Level System Cluster Map

graph TB
    subgraph CHARACTER["Character Domain (GURPS-Adapted)"]
        ATTR[Attributes\nST/DX/IQ/HT]
        ATLAS[Skill Atlas]
        ADVDIS[Advantages &\nDisadvantages]
        SKILLS[Active Skills]
        STANCE[Combat Stances]
        DEFENSE[Active Defenses\nDodge/Parry/Block]
        FP[Fatigue Points]
        WOUND[Wounds & Injuries]
        CREW[Crew/Companions]
        ORIGIN[Character Origin]
    end

    subgraph WORLD["World & Content Domain"]
        CAMP[Campaign\n15 Chapters]
        NCHART[Nautical Chart\nEndgame Atlas]
        ISLAND[Island/Dungeon\nGeneration]
        NAVCOMBAT[Naval Combat]
        PORTS[Port Towns\n& Havens]
        VOYAGE[Voyage System\nSeasons]
        BOSS[Boss Encounters]
        WEATHER[Weather &\nSea State]
        TREASURE[Treasure System]
        EXPLORE[Exploration &\nDiscovery]
        FACTION[Faction System]
        EVENTS[World Events]
    end

    subgraph ECONOMY["Economy Domain"]
        CURR[Currency System\nDoubloons/PoE/Goods]
        CRAFT[Crafting\nDisciplines]
        MODS[Modifier System]
        TRADE[Trade System]
        LOOT[Loot Generation]
        FILTER[Loot Filter]
        VENDOR[Vendor/Fence]
    end

    subgraph NAVAL["Naval Domain"]
        SHIPS[Ship Types\n& Classes]
        SHIPCUST[Ship\nCustomization]
        SHIPCOMBAT[Ship Combat\nSystem]
        SHIPDMG[Ship Damage\nModel]
        FLEET[Fleet\nManagement]
        HARBOR[Port/Harbor\nSystem]
        SEANAV[Sea Navigation]
        TRANSITION[Seamless\nTransitions]
    end

    subgraph INFRA["Infrastructure Domain"]
        CLIENT[Client Engine]
        SERVER[Server\nArchitecture]
        NET[Networking]
        AUTH[Auth & Session]
        INST[Instance\nManagement]
        SEC[Security]
        MTX[Monetization]
        SOCIAL[Social Systems]
        VISAUDIO[Visual/Audio\nPipeline]
        UI[UI/UX Layer]
    end

    %% Cross-domain critical connections
    ATTR -->|derived stats| DEFENSE
    SKILLS -->|attack rolls| STANCE
    STANCE -->|modifies| DEFENSE
    ATLAS -->|unlocks| SKILLS
    ATLAS -->|unlocks| ADVDIS
    FP -->|resource for| SKILLS
    WOUND -->|consequences of| DEFENSE

    LOOT -->|items with| MODS
    MODS -->|modified by| CRAFT
    CRAFT -->|uses| CURR
    CURR -->|traded via| TRADE
    NCHART -->|generates| ISLAND
    VOYAGE -->|injects into| NCHART
    BOSS -->|unlocked via| NCHART

    SHIPS -->|stats for| SHIPCOMBAT
    SHIPCUST -->|equips| SHIPS
    SHIPCOMBAT -->|damages| SHIPDMG
    CREW -->|operates| SHIPCOMBAT
    SEANAV -->|positions for| SHIPCOMBAT
    WEATHER -->|modifies| SHIPCOMBAT
    WEATHER -->|modifies| SEANAV

    NAVCOMBAT -->|boarding triggers| SKILLS
    SHIPCOMBAT ---|same system| NAVCOMBAT
    FLEET -->|commands| SHIPS

    NET -->|syncs| SERVER
    SERVER -->|validates| CLIENT
    INST -->|hosts| ISLAND
    INST -->|hosts| SEANAV
    SEC -->|validates| NET
    MTX -->|cosmetics only| CLIENT
    SOCIAL -->|crews/parties| CREW

    FACTION -->|modifies| TRADE
    FACTION -->|controls| PORTS
    PORTS ---|same as| HARBOR
    EXPLORE -->|reveals| NCHART
    TREASURE -->|found via| EXPLORE
    EVENTS -->|shifts| FACTION

Diagram 2: Character Build Systems (GURPS-Adapted)

graph LR
    ORIGIN[Character Origin\ne.g., Buccaneer] -->|starting attributes\n& skills| ATTR[Attributes\nST 11 / DX 12 / IQ 10 / HT 11]
    ATTR -->|derives| SECONDARY[Secondary Stats\nHP 11 / FP 11 / Will 10\nPer 10 / Speed 5.75\nDodge 8 / Move 5]

    ORIGIN -->|starting position| ATLAS[Skill Atlas\nPoint-Buy Map]
    ATLAS -->|attribute nodes| ATTR
    ATLAS -->|skill ranks| SKILLSET[Active Skills\nSwordsmanship 14\nGunnery 12\nNavigation 11]
    ATLAS -->|advantage unlocks| ADVS[Advantages\nCombat Reflexes\nHigh Pain Threshold]

    SECONDARY -->|defense bases| DEFCALC[Defense Totals\nDodge 9 w/CR\nParry 10\nBlock 9]
    ADVS -->|defense bonuses| DEFCALC
    SKILLSET -->|Parry = skill/2+3| DEFCALC

    SECONDARY -->|resource pools| POOLS[HP Pool: 11\nFP Pool: 13\nwith Extra FP]
    ADVS -->|pool modifiers| POOLS

    GEAR[Equipped Items\nCutlass, Leather Armor\nBuckler, Flintlock] -->|weapon stats| DMGPROFILE[Damage Profile\nSwing 1d+2 cut\nThrust 1d imp]
    GEAR -->|armor DR| DEFCALC
    GEAR -->|shield DB| DEFCALC
    GEAR -->|stat bonuses| ATTR

    DISADVS[Disadvantages\nCode of Honor: Pirate\nOverconfidence\nGreed] -->|story hooks| NARRATIVE[Personal Storylines\nFaction Interactions]
    DISADVS -->|mechanical effects| SKILLSET
    DISADVS -->|Atlas shortcuts| ATLAS

    CREW_COMP[Crew Companions\nSurgeon / Gunner] -->|party support| DEFCALC
    ATLAS -->|captain nodes| CREW_COMP

    SKILLSET -->|combat skills feed| DMGPROFILE
    DMGPROFILE -->|used by| STANCES[Combat Stances\nAll-Out Attack\nDefensive Attack\netc.]
    STANCES -->|modifies| DEFCALC

Diagram 3: Combat/Damage Pipeline (GURPS 3d6 Adapted for Real-Time)

flowchart TD
    INPUT[Player Input:\nAttack Command + Target] --> STANCECHECK{Current Stance?}
    STANCECHECK -->|All-Out Attack| AOAMOD[+4 to hit\nor +2 damage\nNo Active Defenses]
    STANCECHECK -->|Committed Attack| CAMOD[+2 to hit\n-2 to defenses]
    STANCECHECK -->|Defensive Attack| DAMOD[-2 to damage\n+1 to one defense]
    STANCECHECK -->|Normal Attack| NORMALMOD[No modifiers]

    AOAMOD --> FPCHECK{FP Available?}
    CAMOD --> FPCHECK
    DAMOD --> FPCHECK
    NORMALMOD --> FPCHECK

    FPCHECK -->|sufficient FP| ATTACKROLL[Attack Roll\n3d6 vs Effective Skill\nSkill + Stance Mods\n- Range - Conditions]
    FPCHECK -->|low FP| PENALTY[Apply Fatigue Penalty\n-1 per FP below 3\nthen Attack Roll]
    PENALTY --> ATTACKROLL

    ATTACKROLL --> ROLLEVAL{Roll Result?}
    ROLLEVAL -->|3-4: Critical Hit| CRITTABLE[Critical Hit Table\nTriple Damage / Max Damage\nStun / Knockdown / Cripple]
    ROLLEVAL -->|roll <= skill: Hit| HITLOCATION[Hit Location Roll\n3d6 on Location Table\nor Called Shot]
    ROLLEVAL -->|roll > skill: Miss| MISS[Attack Misses]
    ROLLEVAL -->|17-18: Critical Miss| CRITMISS[Critical Miss Table\nDrop Weapon / Fall\nHit Self / Hit Ally]

    CRITTABLE --> DEFENSECHECK
    HITLOCATION --> DEFENSECHECK{Defender Active Defense?}

    DEFENSECHECK -->|Dodge: 3d6 vs Dodge| DODGEROLL[Dodge Roll\nIncludes dodge-roll\ni-frame animation]
    DEFENSECHECK -->|Parry: 3d6 vs Parry| PARRYROLL[Parry Roll\nWeapon-dependent\nUnbalanced: -1 after 1st]
    DEFENSECHECK -->|Block: 3d6 vs Block| BLOCKROLL[Block Roll\nShield-dependent\nDB applies]
    DEFENSECHECK -->|No Defense\nAll-Out Attack| NODEF[Defense Skipped]
    DEFENSECHECK -->|Critical Hit| NODEF

    DODGEROLL -->|success| DEFENDED[Attack Negated\nNo Damage]
    PARRYROLL -->|success| DEFENDED
    BLOCKROLL -->|success| DEFENDED

    DODGEROLL -->|failure| RAWDMG
    PARRYROLL -->|failure| RAWDMG
    BLOCKROLL -->|failure| RAWDMG
    NODEF --> RAWDMG[Calculate Raw Damage\nWeapon Dice + ST Bonus\n+ Stance Bonus]

    RAWDMG --> DRCHECK[Apply DR\nArmor DR at Hit Location\n+ Innate DR from Advantages]
    DRCHECK --> PENETRATING{Penetrating Damage\n= Raw - DR}
    PENETRATING -->|0 or less| NOPEN[No Penetration\nMinimal Bruising]
    PENETRATING -->|> 0| WOUNDMOD[Apply Wound Modifier\nCutting: x1.5\nImpaling: x2\nCrushing: x1\nPi-: x0.5 / Pi+: x1.5]

    WOUNDMOD --> HPLOSS[Apply to HP\nCheck Major Wound\nif damage > HP/2]
    HPLOSS --> SHOCKCHECK{Major Wound?}
    SHOCKCHECK -->|yes| SHOCK[Shock Penalty\n-4 to DX/IQ\nnext turn\nunless High Pain Threshold]
    SHOCKCHECK -->|no| MINORSHOCK[Minor Shock\n-1 per point\nnext turn]

    HPLOSS --> DEATHCHECK{HP <= 0?}
    DEATHCHECK -->|yes| HTROLL[Death Check\n3d6 vs HT\n+ Hard to Kill bonus\nFail = Collapse/Death]
    DEATHCHECK -->|no| BLEEDCHECK

    SHOCK --> BLEEDCHECK{Cutting/Impaling?}
    MINORSHOCK --> BLEEDCHECK
    BLEEDCHECK -->|yes| BLEED[Bleeding Applied\n1 HP/minute\nuntil First Aid]
    BLEEDCHECK -->|no| DONE[Damage Resolved]
    BLEED --> DONE

    style MISS fill:#555,color:#fff
    style CRITMISS fill:#800,color:#fff
    style DEFENDED fill:#060,color:#fff
    style CRITTABLE fill:#c44,color:#fff
    style HTROLL fill:#800,color:#fff
    style NOPEN fill:#363,color:#fff

Diagram 4: Economy Loop

graph TD
    ENCOUNTER[Combat Encounter\nMonster / Ship / Dungeon] -->|drop tables| DROP[Loot Drop\nItems / Currency / Materials]
    DROP -->|low value| VENDOR[Sell to Vendor/Fence\n→ Doubloons]
    DROP -->|currency| CURRSTOCK[Player Currency Stock\nDoubloons / PoE / Salvage]
    DROP -->|good item| EVALUATE{Worth Crafting\nor Trading?}

    EVALUATE -->|sell| PORTMARKET[Port Marketplace\nList at Price]
    EVALUATE -->|craft| CRAFT[Crafting Operation\nBlacksmith / Alchemy\nCurrency Consumed]
    EVALUATE -->|salvage| SALVAGE[Salvage for Materials\n→ Crafting Components]
    CRAFT -->|improved item| EVALUATE

    PORTMARKET -->|buyer purchases| P2PTRADE[Player Trade\nDirect or Automated]
    P2PTRADE -->|currency received| CURRSTOCK
    P2PTRADE -->|item delivered| BUYERCHAR[Buyer's Character\nor Ship]

    CURRSTOCK -->|crew salaries| CREWPAY[Crew Wages\nDoubloon Drain]
    CURRSTOCK -->|ship repairs| REPAIRS[Ship Repairs\nPort Services]
    CURRSTOCK -->|chart progression| CHARTCOST[Nautical Chart\nRegion Unlocking]
    CURRSTOCK -->|high-end crafting| CRAFT
    CURRSTOCK -->|buy from market| PORTMARKET
    CURRSTOCK -->|buy from smuggler| BLACKMARKET[Black Market\nRestricted Goods]

    CHARTCOST -->|unlocks regions| NCHART[Nautical Chart Region\nScaled Encounters]
    NCHART -->|harder encounters| ENCOUNTER
    CREWPAY -->|better crew| CREWPOWER[Crew Effectiveness\nBetter Naval Combat]
    CREWPOWER --> ENCOUNTER
    REPAIRS -->|seaworthy ship| SHIPREADY[Ship at Full Capacity]
    SHIPREADY --> ENCOUNTER
    BUYERCHAR -->|stronger gear/ship| ENCOUNTER

    SALVAGE -->|materials for| CRAFT

    SMUGGLING[Smuggling Runs\nCross-Region Arbitrage] -->|trade goods| CURRSTOCK
    BLACKMARKET -->|faction goods| SMUGGLING

    TREASURE[Treasure Maps\nBuried/Sunken] -->|discovered via| ENCOUNTER
    TREASURE -->|excavated| DROP

    style BLACKMARKET fill:#336,color:#fff
    style P2PTRADE fill:#363,color:#fff
    style CREWPAY fill:#633,color:#fff
    style SMUGGLING fill:#336,color:#fff

Diagram 5: Content Progression (Campaign Through Endgame)

flowchart LR
    NEW[New Character\nChoose Origin] --> CH1[Chapters 1-3\nCaribbean Coast\nLearn Core Combat\nFirst Ship: Pinnace]
    CH1 --> CH2[Chapters 4-6\nOpen Waters\nNaval Combat Intro\nShip Upgrade: Sloop]
    CH2 --> CH3[Chapters 7-9\nFaction Wars\nFaction Allegiance\nShip Upgrade: Brigantine]
    CH3 --> CH4[Chapters 10-12\nDeep Waters\nMythic Encounters\nShip Upgrade: Frigate]
    CH4 --> CH5[Chapters 13-15\nThe Maelstrom\nFinal Boss Arc\nShip Upgrade: Galleon]

    CH5 -->|endgame begins| CHARTLOW[Nautical Chart\nCoastal Waters\nTier 1-4 Regions]
    CHARTLOW --> CHARTMID[Open Seas\nTier 5-8 Regions\nTrading Routes]
    CHARTMID --> LEGENDARY[Legendary Waters\nTier 9-12\nMythic Regions]
    LEGENDARY --> UNCHARTED[Uncharted Depths\nTier 13-16\nEndgame Pinnacle]

    CHARTMID -->|unlocks| FLEET_END[Fleet Management\nMultiple Ships\nNPC Captains]
    CHARTMID -->|side content| TREASURE_HUNT[Treasure Hunting\nBuried Hoards\nSunken Ships]
    LEGENDARY -->|boss progression| SEALORDS[Sea Lords\nLegendary Pirates\n4 Regional Bosses]
    SEALORDS --> KRAKEN[The Kraken\nPinnacle Boss 1]
    LEGENDARY -->|mythic bosses| LEVIATHAN[The Leviathan\nPinnacle Boss 2]
    UNCHARTED -->|ultimate| MAELSTROM[The Maelstrom\nUber Pinnacle\nFinal Challenge]

    CHARTLOW -->|side content| SMUGGLING_END[Smuggling Network\nBlack Market Access]
    CHARTMID -->|side content| ARENA[Port Arena\nPvP Duels]
    LEGENDARY -->|repeatable| FARMING[Boss Drop\nFarming Loop]
    FARMING -->|materials for| SEALORDS

    CH3 -->|first Voyage eligible| VOYAGE[Active Voyage\nSeasonal Content]
    VOYAGE -->|injects into| CHARTMID
    VOYAGE -->|voyage boss| VOYAGEBOSS[Voyage\nPinnacle Boss]

    style MAELSTROM fill:#800,color:#fff
    style KRAKEN fill:#800,color:#fff
    style LEVIATHAN fill:#800,color:#fff
    style VOYAGEBOSS fill:#660,color:#fff

Diagram 6: Naval Systems

graph TB
    subgraph SHIP_BUILD["Ship Building & Customization"]
        ACQUIRE[Ship Acquisition\nPurchase / Capture / Quest]
        CLASS[Ship Class Selection\nPinnace → Man-o'-War]
        HULL[Hull Customization\nArmor / Speed / Draft]
        SAILS[Sail Configuration\nSpeed / Maneuverability / Wind Profile]
        CANNONS[Cannon Loadout\nPort / Starboard / Bow / Stern\nType: Chain / Grape / Bar / Ball]
        FIGURE[Figurehead\nPassive Bonuses\nMorale / Speed / Damage]
        QUARTERS[Crew Quarters\nCapacity / Morale Bonus]
        CARGO[Cargo Hold\nStorage / Smuggling Compartments]
        SPECIAL[Special Equipment\nDiving Bell / Telescope / Ram]
    end

    subgraph NAVAL_COMBAT["Naval Combat"]
        ENGAGE[Engagement\nDetection → Pursuit/Flee]
        POSITION[Positioning\nWind Gauge / Range / Angle]
        BROADSIDE[Broadside Volley\nGunnery Skill + Cannon Type\nvs Target Ship]
        BOARDING[Boarding Action\nGrapple → Crew vs Crew\nPersonal Combat on Deck]
        RAMMING[Ram Attack\nShip ST vs Hull DR\nRisk to Both Ships]
        MANEUVER[Tactical Maneuvers\nNavigation Skill\nCrossing the T / Rake]
        RETREAT[Retreat/Pursuit\nSpeed Contest\nWind Advantage]
    end

    subgraph DAMAGE_MODEL["Ship Damage"]
        HULLDMG[Hull Breach\nFlooding / Sinking Timer]
        MASTDMG[Mast Damage\nSpeed Reduction / Dismasting]
        SAILDMG[Sail Damage\nManeuver Penalty]
        CANNDMG[Cannon Destruction\nFirepower Loss]
        CREWCAS[Crew Casualties\nReduced Manning]
        FIRE[Fire Spread\nProgressive Damage\nCrew Must Fight Fire]
    end

    subgraph FLEET_OPS["Fleet Operations"]
        FLEETFORM[Fleet Formation\nLine / Wedge / Screen]
        NPCCAPT[NPC Captains\nAssign to Ships\nAI Behavior Orders]
        CONVOY[Convoy Missions\nProtect Merchant Ships]
        FLEETBATTLE[Fleet vs Fleet\nLarge-Scale Engagement]
    end

    ACQUIRE --> CLASS
    CLASS --> HULL
    CLASS --> SAILS
    CLASS --> CANNONS
    CLASS --> FIGURE
    CLASS --> QUARTERS
    CLASS --> CARGO
    CLASS --> SPECIAL

    HULL --> ENGAGE
    SAILS --> POSITION
    CANNONS --> BROADSIDE
    QUARTERS --> BOARDING
    SPECIAL --> RAMMING

    ENGAGE --> POSITION
    POSITION --> BROADSIDE
    POSITION --> MANEUVER
    BROADSIDE --> HULLDMG
    BROADSIDE --> MASTDMG
    BROADSIDE --> SAILDMG
    BROADSIDE --> CANNDMG
    BROADSIDE --> CREWCAS
    BROADSIDE --> FIRE
    MANEUVER --> POSITION
    MANEUVER --> BOARDING
    RAMMING --> HULLDMG
    BOARDING -->|triggers personal combat| PERSONAL[Personal Combat\non Enemy Deck]

    HULLDMG -->|ship sinking| CAPTURE[Capture or Sink\nLoot / Salvage]
    CREWCAS -->|crew depleted| SURRENDER[Surrender\nCapture Ship]
    FIRE -->|uncontrolled| HULLDMG

    MASTDMG --> RETREAT
    SAILDMG --> RETREAT

    FLEET_OPS -.->|commands| ENGAGE
    NPCCAPT -->|AI controls| MANEUVER
    FLEETFORM -->|determines| POSITION

    style PERSONAL fill:#363,color:#fff
    style CAPTURE fill:#336,color:#fff
    style FIRE fill:#c44,color:#fff
    style HULLDMG fill:#633,color:#fff

Diagram 7: Technical Infrastructure

graph TB
    subgraph CLIENT_SIDE["Client Side"]
        PLAYERINPUT[Player Input\nKB/Mouse/Controller]
        RENDERER[Custom Engine\nDX12 / Vulkan\nDeferred + PBR]
        OCEAN[Ocean Renderer\nWave Simulation\nReflections]
        PREDICT[Predictive Mode\nor Lockstep Gate]
        ASSETS[Asset Archive\nDisk / SSD Load]
        LOOTFILT[Loot Filter\nScript Engine]
        UIFRAME[UI Framework\nHUD / Skill Atlas\nNautical Chart]
        AUDIO[FMOD Audio\n3D Spatial\nAdaptive Music]
    end

    subgraph NETWORK["Network Layer"]
        GW[Gateway\nDDoS Shield\n+ Router]
        TCP_CONN[TCP Connection\nDelta Updates]
        TRANSITION_PROTO[Transition Protocol\nSea ↔ Land\nSeamless Handoff]
    end

    subgraph SERVER_SIDE["Server Side"]
        AUTH[Auth Service\nOAuth 2.1\nSession Mgmt]
        ACCTAUTH[Account Authority\nCharacter + Ship\n+ Item DB]
        SEA_INST[Sea Instance Servers\nNaval Simulation\n10-20 Hz Tick]
        LAND_INST[Land Instance Servers\nCombat Simulation\n20-30 Hz Tick]
        TRADE_SVC[Trade Service\nPort Marketplace\nSearch Index]
        VOYAGE_SVC[Voyage Service\nSeasonal State\nLeaderboard]
        SOCIAL_SVC[Social Service\nCrew/Party/Chat\nPvP Matchmaking]
        WEATHER_SVC[Weather Service\nGlobal Weather State\nRegion Patterns]
        FACTION_SVC[Faction Service\nReputation Tracking\nTerritory Control]
    end

    subgraph DB["Persistence Layer"]
        CHARDB[(Character DB\nAttributes, Skills\nAtlas Allocation)]
        SHIPDB[(Ship DB\nComponents, Damage\nCrew Assignment)]
        ITEMDB[(Item DB\nModifier Records)]
        STASHDB[(Cargo/Stash DB\nTab Contents)]
        CHARTDB[(Nautical Chart DB\nDiscovery State\nRegion Mods)]
        FACTIONDB[(Faction DB\nReputation Scores)]
    end

    PLAYERINPUT --> PREDICT
    PREDICT --> GW
    GW --> AUTH
    AUTH --> SEA_INST
    AUTH --> LAND_INST

    SEA_INST --> TCP_CONN
    LAND_INST --> TCP_CONN
    TCP_CONN --> RENDERER
    TCP_CONN --> OCEAN
    ASSETS --> RENDERER
    ASSETS --> OCEAN

    SEA_INST <--> TRANSITION_PROTO
    LAND_INST <--> TRANSITION_PROTO
    TRANSITION_PROTO --> GW

    SEA_INST --> ACCTAUTH
    LAND_INST --> ACCTAUTH
    ACCTAUTH --> CHARDB
    ACCTAUTH --> SHIPDB
    ACCTAUTH --> ITEMDB
    ACCTAUTH --> STASHDB
    ACCTAUTH --> CHARTDB

    TRADE_SVC --> ITEMDB
    VOYAGE_SVC --> SEA_INST
    VOYAGE_SVC --> LAND_INST
    SOCIAL_SVC <--> SEA_INST
    SOCIAL_SVC <--> LAND_INST
    WEATHER_SVC --> SEA_INST
    WEATHER_SVC --> LAND_INST
    FACTION_SVC --> FACTIONDB

    LOOTFILT --> RENDERER
    UIFRAME --> RENDERER
    AUDIO --> RENDERER

4. Emergent Complexity Analysis

Level 1: Individual System Complexity

Each system in Salt & Steel carries meaningful internal complexity that rewards mastery. The Skill Atlas contains hundreds of nodes across thematic regions, each offering attribute bonuses, skill ranks, technique unlocks, and advantage acquisitions. The ship customization system alone has 8+ component categories, each with tiered options that interact with ship class constraints. The GURPS 3d6 bell curve creates a probability landscape fundamentally different from d20 or flat-random systems — a +1 bonus near the center of the curve (10-11 target) is worth more than a +1 at the extremes, creating non-linear value curves for every stat investment.

The combat stance system, even in isolation, demands tactical thinking: choosing between All-Out Attack (maximum damage, zero defense) and Defensive Attack (reduced damage, improved defense) is a per-engagement decision with life-or-death consequences. The GURPS foundation ensures that no single system is trivial.

Level 2: Pairwise Interaction Complexity

When two systems interact, the complexity multiplies. Consider the Advantage/Disadvantage system interacting with Combat Stances: a character with the Berserk disadvantage is forced into All-Out Attack when wounded, removing their active defenses — but if they also have High Pain Threshold (advantage), they ignore the shock penalties that would normally compound the danger. The Disadvantage creates vulnerability, the Advantage partially compensates, and the player must build around both.

The Fatigue-Stance interaction creates another layer: aggressive stances burn FP faster, but FP depletion applies attribute penalties that reduce both attack skill and defense values. A character who fights too aggressively exhausts themselves, becoming less effective at both offense and defense — a natural feedback loop that prevents pure glass-cannon play without explicit HP-cost mechanics.

Ship class interacting with Nautical Chart creates gear-check progression: deep ocean chart regions require Frigates or larger, but Frigates require substantial crew (salary costs) and dock only at deep-water ports (limiting resupply options). The ship progression is not linear power growth — it is a tradeoff between capability and operational cost.

Level 3: N-ary Build Synergies

The deepest complexity emerges when three or more systems interact:

• Combat Reflexes + Enhanced Dodge + Acrobatic Dodge technique: Combat Reflexes (advantage, via Atlas) grants +1 to all active defenses and +6 to recover from surprise. Enhanced Dodge (advantage) grants another +1 to Dodge. The Acrobatic Dodge technique (skill, via Atlas) allows substituting Acrobatics skill for Dodge when there is room to maneuver. A character with Acrobatics-16 and these two advantages has an effective Dodge of (16/2 + 3 + 1 + 1) = 13 — succeeding on a 3d6 roll of 13 or less (83.8% success rate). This is a three-system synergy that creates an almost untouchable dodge-focused build archetype, but only functions on land with room to maneuver (fails on ship decks, in narrow corridors, and when encumbered).

• Weapon Master + All-Out Attack (Strong) + High ST + Cutting weapon: Weapon Master (advantage) adds +2 damage per die. All-Out Attack Strong (stance) adds +2 flat damage. A character with ST 16 (swing 2d+2) wielding a cutlass (+1 cutting) swings for 2d+5 cutting with Weapon Master, or 2d+7 cutting in All-Out Attack Strong. After the cutting x1.5 wound modifier, average penetrating damage against DR 2 armor is (7+5-2) x 1.5 = 15 HP — enough to one-shot most human-scale enemies. But All-Out Attack removes all active defenses, making the character vulnerable to counterattack. Four systems (attributes, advantages, stances, weapon type) producing a glass-cannon melee archetype.

• The "Juiced Chart Region" compound: Nautical Chart region danger modifiers (chart system) multiply encounter density (region scaling) which multiplies Voyage mechanic activations (voyage system) which generate additional encounters that drop loot scaled by the region danger modifier. A fully modified Tier 16 Uncharted region during an active Voyage with fleet support generates 20-50x the loot of an unmodified Tier 1 coastal region. This is the economic engine that drives endgame wealth accumulation — and its multiplicative nature means small improvements to any single multiplier have outsized effects on total output.

• Naval-to-Personal Combat Transition: A player boards an enemy Galleon (naval combat) using a grappling hook (seamanship skill + ship equipment), transitioning to personal combat on the enemy deck (combat system) where their crew companions (crew system) fight alongside them against enemy crew (AI system), while the two ships remain grappled and taking damage from each other's remaining gunners (ship damage model) and a storm is reducing everyone's combat effectiveness (weather system). Six systems interacting simultaneously, creating emergent tactical decisions (do you fight the enemy captain quickly, or go below deck to sabotage their hull?).

Level 4: Meta-Game Complexity

At the system level, the economy creates emergent complexity that extends beyond what designers can fully predict. The dual nature of currencies (crafting utility + trade medium) means that efficient crafting directly competes with market participation — spending Pieces of Eight on high-end crafting removes them from circulation, affecting their exchange rate against Doubloons. Voyage-specific materials create time-limited supply shocks that reward players who anticipate demand.

The Crew salary system creates a persistent economic drain proportional to fleet size, preventing unlimited fleet accumulation and creating a natural scale ceiling for all but the most economically efficient players. This interacts with the Trade system (larger fleets generate more plunder but cost more to maintain) and the Faction system (faction reputation unlocks efficient elite crew that provide more value per salary Doubloon).

The existence of necessary community tools (build planners, trade indexers, Skill Atlas optimizers) — following PoE's pattern — indicates that the system's combinatorial complexity will exceed what any in-game UI can fully represent. Designing for this from the start (providing APIs, supporting community tool development) is an architectural requirement, not an afterthought.

5. System Coupling Assessment

Tightly Coupled Pairs (Breaking One Breaks the Other)

• Attributes ↔ Active Defenses: The entire defense calculation chain (Dodge from Basic Speed from DX+HT, Parry from weapon skill from DX, Block from shield skill from DX) is hard-wired to attribute values. Any change to the attribute system cascades through every defense calculation for every character.
• Ship Class ↔ Naval Combat: Ship combat stats (cannon slots, hull points, speed, crew capacity) are entirely derived from ship class. A change to ship class definitions rewrites the entire naval combat balance.
• Damage Calculation ↔ Server Authority: All 3d6 rolls, damage calculations, and defense resolutions must be server-validated. Any disruption to server-side calculation breaks combat integrity and enables exploits.
• Nautical Chart ↔ Instance Management: Chart regions are instantiated as sea zones. If instance creation fails, chart exploration is blocked regardless of chart state. This is the PoE atlas/instance coupling directly translated.
• Crew System ↔ Naval Combat: Ships without adequate crew cannot fire cannons, perform damage control, or execute boarding actions. Crew system failures would make naval combat non-functional.
• Fatigue System ↔ Active Skills: All abilities cost FP. If the FP system is disrupted, the entire skill/ability economy collapses — characters either have infinite ability use or none.

Moderately Coupled Systems (Degraded Without, Not Broken)

• Skill Atlas ↔ Advantage System: Advantages are primarily acquired through Atlas progression. Without the Atlas, characters can still function with origin-granted advantages, but build depth is severely limited.
• Weather System ↔ Naval Combat: Weather modifies naval combat significantly (wind, visibility, hull stress) but naval combat functions at base parameters without weather input.
• Faction System ↔ Trade System: Faction reputation modifies prices and access but trade functions at base rates without faction integration.
• Voyage System ↔ Nautical Chart: Voyages inject content into chart regions, enriching the endgame. Without active Voyages, the chart still functions with base content — Voyages are additive.
• Loot Filter ↔ Loot Generation: Filters affect only display. In endgame density, filters become operationally necessary, but loot still drops and functions without filtering.
• Crew Companions ↔ Land Combat: Crew companions enhance land combat but characters are fully functional solo. The coupling is one-way enhancement.
• Treasure System ↔ Exploration System: Treasure maps are discovered through exploration, but treasure can also be found through direct loot drops and quest rewards.

Loosely Coupled Systems (Optional Integration)

• Social Systems ↔ Core Gameplay: Crews (guilds) provide social benefits and shared resources but are not required for any gameplay progression. Solo play is fully viable.
• PvP ↔ PvE Systems: PvP naval duels and port arena share combat infrastructure but are mechanically siloed from PvE progression. PvP rewards are cosmetic or prestige-based.
• Cosmetic MTX ↔ Gameplay: Ship skins, weapon effects, and character outfits use the same rendering pipeline but have zero mechanical impact. This is the ethical F2P firewall.
• World Events ↔ Individual Progression: Dynamic world events provide optional group content but individual progression does not require event participation.
• Fleet Management ↔ Solo Play: Fleet operations are an endgame extension. Players who prefer a single ship experience can complete all content with a single well-built vessel.

Architectural Decoupling Decisions (Learned from PoE)

Salt & Steel makes several deliberate decoupling decisions informed by PoE's architectural history:

• Skills are learned, not socketed: Unlike PoE 1's gem-socket coupling (where skills were tied to equipment socket links), Salt & Steel's active skills are character knowledge, decoupled from equipment. This eliminates the "6-link" problem entirely — no single equipment milestone dominates character power.
• Currency crafting functions are independent of trade value: Each currency type has a defined crafting function regardless of its trade value. This prevents the PoE scenario where a currency's crafting utility is overshadowed by its trade value (e.g., Exalted Orbs being too valuable to "waste" on actual slamming).
• Voyages do not require full economy resets: Unlike PoE leagues which reset all economic progress, Voyages inject content into the existing economy. This reduces the "league start or nothing" pressure that fragments PoE's playerbase.
• Naval and personal combat share GURPS foundations: Both combat layers use the same underlying mechanics (3d6 rolls, skill-based resolution, active defenses), preventing the architectural divergence that would occur if naval combat used a completely separate engine.

6. The Architecture as a Whole

Salt & Steel's architecture is designed around three gravitational centers rather than PoE's one:

1. The GURPS Mechanical Core — The 3d6 bell curve, point-buy attributes, skill system, advantage/disadvantage framework, and active defense model form the mathematical foundation. Every character interaction, from swordfighting to ship navigation to crafting, resolves through GURPS-derived mechanics. This creates a unified mechanical language across all systems — a character's Swordsmanship skill and their Gunnery skill use the same resolution mechanic, making the system internally consistent even as it spans radically different gameplay contexts.

2. The Dual-Scale Combat System — Personal combat (character vs. monsters on land and ship decks) and naval combat (ship vs. ship on the sea) operate at different spatial and temporal scales but share mechanical DNA. This is Salt & Steel's most architecturally ambitious feature — maintaining two simultaneous combat layers that can transition seamlessly (boarding actions) and interact concurrently (ships exchanging broadsides while boarding parties fight on deck). The infrastructure must support both scales within the same instance or across linked instances.

3. The Sea-Land Continuum — Unlike PoE's purely instanced world, Salt & Steel must handle seamless transitions between sea zones (large, shared, naval-scale) and land instances (smaller, private/party, personal-scale). The networking model, instance management, and rendering engine must all accommodate this duality. Sea zones are closer to MMO-style shared spaces (multiple ships visible, weather affecting all occupants) while land instances follow PoE's model (private per party, procedurally generated).

The most architecturally significant decisions are:

• Server-authoritative 3d6: All GURPS rolls are server-generated. The bell curve is sacred — client-side prediction can animate attacks and defenses, but the actual 3d6 roll happens on the server. This is computationally more expensive than PoE's flat-random calculations because the bell curve concentrates results around the mean, requiring higher precision in the probability model.
• No economy resets: Voyages add content without wiping progress. This changes the economic dynamics fundamentally — currency accumulates across Voyages, creating different inflationary pressures than PoE's league-reset model. The crew salary system, ship maintenance costs, and chart region modification costs serve as currency sinks to counteract accumulation.
• Crew as economic drain: The Crew system creates a persistent, scaling operating cost that provides a natural ceiling on fleet expansion and incentivizes economic engagement. This is a deliberate sink that PoE lacks — PoE's economy has no ongoing maintenance costs for character power.
• The Skill Atlas as character identity: The Atlas replaces both PoE's passive tree and its skill gem system as the primary character identity structure. A character's Atlas allocation defines their skills, advantages, and attribute bonuses — it is the single most consequential set of decisions in build creation.

The result is a system with greater total surface area than PoE (the naval domain adds roughly 30% more systems) but with stronger internal consistency (GURPS provides a unifying mechanical language that PoE's organic growth never had). The risk is in the dual-scale combat and sea-land transition systems, which represent engineering challenges PoE never faced and which have no proven ARPG precedent at this scale.

Cross-references: design/00-vision/pillars.md, design/02-characters/attribute-system.md, design/02-characters/skill-atlas.md, design/03-combat-and-skills/damage-pipeline.md, design/05-economy/currency-system.md, design/07-endgame/nautical-chart.md, design/10-technical-architecture/server-architecture.md, design/16-naval-systems/ship-combat.md