/godot-genre-action-rpg

ARPG Subsystems Deep-Dive (load on demand)

MANDATORY when wiring combat formulas, loot affixes, equipment slots, or area scaling beyond the script catalog. Peer skills own full inventory/ability tutorials — route there after this reference.

Combat damage (diminishing armor)

WHY not linear armor: armor / (armor + K) caps reduction — linear stacking to 100% creates invincible tanks.

Implementation: combat_damage_calculator.gd + stat_reduction_solver.gd.

Hit resolve stays in _physics_process via hitbox_component.gd — enable monitoring only on attack frames; guard multi-hit per swing with a has_hit array.

Progression curve

Damage/HP scaling: base * pow(1.15, level) — linear curves flatten the power fantasy. XP to next level: int(100 * pow(1.5, level - 1)).

Loot generation

loot_generator.gd — weighted rarity table + magic-find bias on rare+. Affix count scales with rarity tier.

Visual differentiation: rarity beams via RenderingServer.instance_geometry_set_shader_parameter — avoid material.duplicate() storms (see Advanced ARPG Meta-Systems in SKILL.md).

Equipment & stats

• Stats live in Resource containers (character_stats_resource.gd) — recalculate only on equip/level/buff change, never every frame.
• duplicate(true) at spawn: deep_stat_duplicator.gd / entity_stat_duplicator.gd.
• Equipment applies flat then percent modifiers, then calls recalculate_stats().

Ability / skill-tree glue

Hotbar abilities → godot-ability-system. Skill-tree unlocks grant AbilityResource to the caster's scene manager — not a global combat Autoload.

Enemy scaling

enemy_area_scaler.gd — level_mult = 1 + (area_level - 1) * 0.15 on vitality/strength and XP reward.

Architecture overview

Progression Autoloads (catalog only)     Scene entities
├── unlock flags / quest state           ├── CharacterBody + components
└── loot tables (data)                   ├── HealthComponent / Hitbox
                                         ├── scene AbilityManager
                                         └── RPGStats Resource (duplicated)

Signals up, calls down — HUD observes; never treat UI SceneTree as inventory truth (threaded_inventory_loader.gd for heavy parses).

Common pitfalls

Reference titles

Diablo / PoE (loot), Elden Ring / Souls (combat telegraphs), Hades (ability cadence), Grim Dawn (build depth).