heros/docs/ARCHITECTURE.md

Architecture

Principles

• Keep rules data-driven.
• Keep battle state independent from rendering.
• Build one complete vertical slice before expanding systems.
• Prefer simple Godot nodes and GDScript until a system proves it needs more structure.

Current Layout

• project.godot: Godot 4 project configuration.
• scenes/battle_scene.tscn: Main playable battle scene.
• scripts/core/data_catalog.gd: JSON definition loader and deployment hydrator.
• scripts/core/campaign_state.gd: Thin campaign save state for gold, inventory, roster, completed scenarios, and campaign flags.
• scripts/core/battle_state.gd: Battle rules, unit state, turns, AI, and victory checks.
• scripts/scenes/battle_scene.gd: Rendering, input handling, and HUD wiring.
• audio/bgm/*.wav and audio/sfx/*.wav: Placeholder music loops and interface/action stingers.
• data/campaign/campaign.json: Campaign chapter ranges, scenario order, and scenario paths.
• data/defs/*.json: Officers, classes, terrain, items, and skills.
• data/scenarios/*.json: Scenario definitions.

Data Files

• data/defs/classes.json: Class stats, movement types, skill access.
• data/defs/officers.json: Named officer base stats, growth, and default portrait paths.
• data/defs/items.json: Weapons, armor, accessories, and consumables.
• data/defs/skills.json: MP tactic definitions for damage, healing, support, status effects, target rules, and range.
• data/defs/terrain.json: Terrain colors, defense, avoid, and movement costs.
• data/campaign/campaign.json: Chapter ranges, scenario sequence, titles, and resource paths.
• data/scenarios/*.json: Dialogue, deployments, rewards, and branching flags.

Battle Loop

1. Load battle data.
2. Hydrate deployments through DataCatalog.
3. Dispatch battle-start scenario events.
4. Show scenario briefing with the campaign chapter header, battle header, objective summary, chapter overview, manual checkpoint menu, and optional pre-battle shop, Armory, Roster, and Formation setup.
5. Player selects a unit.
6. Briefing completion dispatches battle-begin events, including opening dialogue.
7. Unit moves, attacks, chooses a tactic or consumable item from the side menu, changes equipment, counters, gains EXP, levels up, promotes at class thresholds, or waits. Tactic buttons show MP cost, kind, range, and power, support, debuff, movement modifier, accuracy/evasion modifier, damage-over-time, or action-lock effect. Physical attacks roll hit chance from unit agility and target terrain avoid; misses give reduced EXP. The scene plays placeholder SFX, a short movement slide, low-HP warning rings, hover target preview badges, and floating combat text for core action and UI feedback.
8. Player ends turn.
9. Enemy AI moves, attacks, and can cast damage, healing, support, debuff, movement-modifier, accuracy/evasion-modifier, damage-over-time, or action-lock tactics through the same combat and skill resolvers.
10. Battle checks scenario-defined defeat conditions first, including commander loss and turn limits, then victory conditions such as enemy defeat or reaching a marked destination tile.
11. Turn-start and movement-triggered scenario events run as phases change or units enter marked cells, and may update objectives or deploy reinforcements.
12. On first-time victory, CampaignState snapshots player progression and the battle inventory, applies rewards once, advances current_scenario_id, and writes user://campaign_save.json.
13. If the scenario defines post-battle dialogue, it plays once before the victory result panel opens.
14. The victory result panel summarizes rewards plus saved player level-ups and promotions.
15. If the scenario defines post-battle choices, the result panel waits for the player to select one, then saves the selected flags and optional choice rewards before enabling the next battle.
16. The result panel can load the next scenario, passing saved roster and inventory overlays back into BattleState.
17. Once all campaign scenarios are complete, the battle scene shows a campaign completion panel instead of loading another map.

Save Boundary

BattleState owns tactical runtime fields. CampaignState saves only campaign-facing data: completed scenario ids, gold, inventory counts, joined officers, campaign flags, and a player roster snapshot. It does not save map positions, pre-battle Roster/Formation choices, action flags, temporary status effects, or transient battle occupancy.

Joined officers gate whether requires_joined player deployments are loaded at all. Rewards and post-battle choices can add or remove joined officers without deleting their saved roster snapshot, so a later rejoin can preserve progression. When a save loads, CampaignState scans completed scenarios in campaign order and reapplies only officer join/leave transitions from rewards and the saved applied_post_battle_choices ledger, allowing added recruitment rewards to reach older saves without replaying gold or items. Old saves without the ledger can backfill a choice id only when exactly one completed scenario choice matches saved flags. Roster entries are keyed by officer_id when available, so future scenarios can deploy the same joined officer under different scenario-specific unit_id values. Saved progression overlays final battle stats for now; a later equipment refactor should split base stats from equipment bonuses before adding item leveling or stat recalculation. New battles currently start player units healed to their saved maximum HP/MP. Skill access is carried in roster snapshots, with class defaults still applied for old saves that do not include skills. Promoted class ids are saved in the roster, and the next battle rehydrates class-derived movement, growth, skills, and range from the saved class id before equipment range is recalculated.

Inventory and campaign flags are copied from CampaignState into BattleState when a scenario starts. The pre-battle Chapters overview reads CampaignState chapter progress and can load completed or current battles without mutating the save. The pre-battle Save menu can write the current campaign state to user://campaign_manual_save.json, and loading that checkpoint restores it into user://campaign_save.json before re-entering the same pending-choice, completion, or current-briefing branch as startup. Pre-battle shop stock comes from the loaded scenario's shop.items list plus matching shop.conditional_items blocks, with optional finite limits from item entries or stock maps. Shop purchases and 50% sell-back are campaign transactions: they update saved gold, unequipped inventory, and finite-stock purchase counts immediately, write the save file, and refresh the already-loaded battle inventory before the player begins the battle. Pre-battle Armory equipment changes use the same equipment rules as battle HUD equipment changes, then immediately save merged roster equipment/stat snapshots and inventory stock. Pre-battle Roster uses scenario roster.max_units, roster.required_officers, and roster.required_units to mark optional player deployments as sortie or reserve; reserve units remain in the candidate list but are excluded from board occupancy, drawing, selection, AI targeting, and living-unit victory checks. Non-controllable player units can act as protected escort targets: enemies can attack them and conditions can reference them, but they are skipped by player selection, Armory, Formation, counterattacks, and campaign roster progression snapshots when persist_progression is false. Scenario ai_target_priority nudges enemy movement and damage-skill scoring toward important targets such as envoys without overriding defeat bonuses or range checks. Pre-battle Formation uses the loaded scenario's formation.cells and only mutates current battle unit positions before battle-begin events fire. Destination victory cells from unit_reaches_tile conditions are exposed to the scene for objective overlays and tile info. Movement-triggered unit_reaches_tile events receive the unit that just moved, so ambushes fire on entry rather than from units already standing on a marker. Briefing data can append matching briefing.conditional_lines, and scenario events can use when.campaign_flags to branch dialogue, objective changes, and reinforcements from saved campaign choices. Consumable use can restore HP or MP or cure matching poison/seal/snare statuses, and in-battle item use plus equipment swaps mutate only the battle copy until victory; defeats and restarts do not spend saved items or preserve in-battle gear changes. Post-battle choices write campaign flags only after the result-panel button is pressed; if the player reloads after rewards are saved but before selecting, the pending scenario id restores the victory choice panel without replaying rewards. The next battle button stays locked until the campaign choice save succeeds. Equipment rewards share the same item_id -> count inventory stock, cover weapon, armor, and accessory slots, can be equipped from the side HUD before the selected unit moves or acts, and do not appear in the consumable action menu. Already completed scenarios can be replayed without granting duplicate rewards, choices, replay inventory consumption, save writes, current-scenario advancement, or finite-stock purchases; pre-battle Shop, Armory, Roster, Formation, and Save are disabled on completed-scenario replays to avoid side effects.

The battle scene owns presentation feedback: briefing and result states use menu BGM, briefing headers combine CampaignState chapter ranges, campaign order, and title data with BattleState briefing and objective text, active battles use battle BGM, dialogue lines can show optional portrait textures or speaker-initial fallback panels and can place the portrait on the left or right side of the dialogue panel, board units render low-HP warning rings, HP bar color states, and active support/debuff/poison/seal/snare status pips from battle state fields, hover previews are rendered as target badges from existing BattleState forecast APIs, log/result hooks trigger placeholder SFX, support, debuff, poison, seal, and snare effects use distinct floating feedback colors, BattleState.unit_motion_requested asks the scene to interpolate a unit's draw position during movement, and BattleState.combat_feedback_requested asks the scene to draw transient floating combat text without changing battle rules.

The New Campaign button clears user://campaign_save.json, resets campaign state to the first scenario, and reloads the opening briefing.