fix: golem combat runtime - elemental matchup, enchantment effects, spell damage/cost, armor pierce (issue #313)

docs/circular-deps.txt

@@ -1,4 +1,4 @@
 # Circular Dependencies
-Generated: 2026-06-07T21:06:17.789Z
+Generated: 2026-06-07T21:16:10.397Z
 
 No circular dependencies found. ✅

docs/dependency-graph.json

@@ -1,6 +1,6 @@
 {
   "_meta": {
-    "generated": "2026-06-07T21:06:15.829Z",
+    "generated": "2026-06-07T21:16:08.368Z",
     "description": "Import dependency graph for src/lib/game. Keys are files, values are arrays of files they import.",
     "usage": "To find what a file affects, search for its path in the VALUES. To find what a file depends on, look at its KEY entry."
   },
@@ -203,6 +203,7 @@
     ],
     "crafting-fabricator.ts": [
       "data/fabricator-recipes.ts",
+      "effects/discipline-effects.ts",
       "stores/manaStore.ts",
       "types.ts"
     ],

docs/project-structure.txt

@@ -385,7 +385,10 @@ Mana-Loop/
 │   │   │   │   ├── gameLoopActions.ts
 │   │   │   │   ├── gameStore.ts
 │   │   │   │   ├── gameStore.types.ts
+│   │   │   │   ├── golem-combat-actions.test.ts
 │   │   │   │   ├── golem-combat-actions.ts
+│   │   │   │   ├── golem-combat-helpers.test.ts
+│   │   │   │   ├── golem-combat-helpers.ts
 │   │   │   │   ├── golemancy-actions.ts
 │   │   │   │   ├── golemancy-combat.test.ts
 │   │   │   │   ├── index.ts

src/lib/game/stores/combat-actions.ts

@@ -12,9 +12,9 @@ import { getFloorMaxHP, getFloorElement, getMultiElementBonus, calcDamage, calcM
 import { computeDisciplineEffects } from '../effects/discipline-effects';
 import {
   processGolemMaintenance,
-  processGolemAttacks,
   processGolemManaRegen,
 } from './golem-combat-actions';
+import { processGolemAttacksFromStore } from './golem-combat-helpers';
 import { applyDamageToRoom } from './combat-damage';
 
 // ─── Result Type ───────────────────────────────────────────────────────────────
@@ -306,11 +306,14 @@ export function processCombatTick(
 
     // ─── Golem attacks (spec §11) ───────────────────────────────────────────
     if (activeGolems.length > 0 && floorHP > 0) {
-      const golemResult = processGolemAttacks(
+      const golemResult = processGolemAttacksFromStore(
         activeGolems,
         golemDesigns,
         onDamageDealt,
         golemApplyDamageToRoom,
+        getFloorElement(currentFloor),
+        get,
+        set,
       );
       rawMana = golemResult.rawMana;
       elements = golemResult.elements;

src/lib/game/stores/golem-combat-actions.test.ts

@@ -0,0 +1,347 @@
+// ─── Golem Combat Actions Regression Tests (Issue #313) ────────────────────────
+// Tests the 5 fixes applied to processGolemAttacks:
+// 1. Spell damage uses actual SPELLS_DEF[spellId].dmg * frame.magicAffinity
+// 2. Spell mana cost uses actual SPELLS_DEF[spellId].cost.amount
+// 3. Elemental matchup applied to basic attacks
+// 4. Enchantment effects applied to basic attacks
+// 5. Armor pierce bypasses armor fraction instead of multiplying damage
+
+import { describe, it, expect } from 'vitest';
+import {
+  CORES, FRAMES, MIND_CIRCUITS, GOLEM_ENCHANTMENTS,
+} from '@/lib/game/data/golems';
+import { SPELLS_DEF } from '@/lib/game/constants';
+import type { GolemDesign, SerializedDesign } from '@/lib/game/data/golems/types';
+import type { EnemyState, RuntimeActiveGolem } from '@/lib/game/types';
+import { processGolemAttacks } from './golem-combat-actions';
+import { computeBasicAttackDamage } from './golem-combat-helpers';
+
+// ─── Helpers ──────────────────────────────────────────────────────────────────
+
+function makeDesign(
+  coreId: string,
+  frameId: string,
+  circuitId: string,
+  enchantIds: string[] = [],
+  selectedSpells: string[] = [],
+): GolemDesign {
+  return {
+    id: `test_${coreId}_${frameId}_${circuitId}`,
+    name: `Test ${coreId} ${frameId}`,
+    core: CORES[coreId],
+    frame: FRAMES[frameId],
+    mindCircuit: MIND_CIRCUITS[circuitId],
+    enchantments: enchantIds.map(id => GOLEM_ENCHANTMENTS[id]).filter(Boolean),
+    selectedManaTypes: [],
+    selectedSpells,
+  };
+}
+
+function makeSerialized(design: GolemDesign): SerializedDesign {
+  return {
+    id: design.id,
+    name: design.name,
+    coreId: design.core.id,
+    frameId: design.frame.id,
+    mindCircuitId: design.mindCircuit.id,
+    enchantmentIds: design.enchantments.map(e => e.id),
+    selectedManaTypes: design.selectedManaTypes,
+    selectedSpells: design.selectedSpells,
+  };
+}
+
+function makeActiveGolem(design: GolemDesign, currentMana?: number, attackProgress = 0): RuntimeActiveGolem {
+  return {
+    designId: design.id,
+    summonedFloor: 1,
+    attackProgress,
+    roomsRemaining: 3,
+    currentMana: currentMana ?? design.core.manaCapacity,
+    spellCastIndex: 0,
+  };
+}
+
+function makeEnemy(overrides: Partial<EnemyState> = {}): EnemyState {
+  return {
+    id: 'enemy-1',
+    name: 'Test Enemy',
+    hp: 100,
+    maxHP: 100,
+    armor: 0.2,
+    dodgeChance: 0,
+    element: 'fire',
+    activeEffects: [],
+    effectiveArmor: 0.2,
+    ...overrides,
+  };
+}
+
+// Helper: run processGolemAttacks with attackProgress pre-set to trigger attacks
+function runGolemAttacks(
+  golem: RuntimeActiveGolem,
+  serialized: SerializedDesign,
+  design: GolemDesign,
+  enemy: EnemyState,
+  enemyElement: string,
+  onDamage?: (dmg: number) => { rawMana: number; elements: Record<string, never> },
+) {
+  let capturedDamage = 0;
+  const result = processGolemAttacks(
+    [golem],
+    { [design.id]: serialized },
+    onDamage ?? ((dmg) => { capturedDamage = dmg; return { rawMana: 0, elements: {} }; }),
+    () => ({ floorHP: 50, floorMaxHP: 100, roomCleared: false }),
+    enemyElement,
+    () => enemy,
+    () => {},
+  );
+  return { result, capturedDamage };
+}
+
+// ─── Fix #1 & #2: Spell damage and mana cost ─────────────────────────────────
+
+describe('processGolemAttacks - spell damage and mana cost (fixes #1, #2)', () => {
+  it('uses actual spell damage (SPELLS_DEF.dmg * magicAffinity) not hardcoded 20', () => {
+    const design = makeDesign('basic', 'earth', 'intermediate', [], ['fireball']);
+    const serialized = makeSerialized(design);
+    const spellDef = SPELLS_DEF['fireball'];
+    const frame = FRAMES['earth'];
+    const golem = makeActiveGolem(design, 100, 1.0);
+    const enemy = makeEnemy();
+
+    const expectedSpellDmg = spellDef.dmg * frame.magicAffinity; // 15 * 0.3 = 4.5
+
+    const { capturedDamage } = runGolemAttacks(golem, serialized, design, enemy, 'fire');
+
+    expect(capturedDamage).toBe(expectedSpellDmg);
+    expect(capturedDamage).not.toBe(20 * frame.magicAffinity); // Old buggy value would be 6
+  });
+
+  it('uses actual spell mana cost not hardcoded 10', () => {
+    const design = makeDesign('basic', 'earth', 'intermediate', [], ['fireball']);
+    const serialized = makeSerialized(design);
+    const spellDef = SPELLS_DEF['fireball'];
+    const golem = makeActiveGolem(design, spellDef.cost.amount, 1.0);
+    const enemy = makeEnemy();
+
+    let spellCastCount = 0;
+    processGolemAttacks(
+      [golem],
+      { [design.id]: serialized },
+      () => { spellCastCount++; return { rawMana: 0, elements: {} }; },
+      () => ({ floorHP: 50, floorMaxHP: 100, roomCleared: false }),
+      'fire',
+      () => enemy,
+      () => {},
+    );
+
+    expect(spellCastCount).toBeGreaterThan(0);
+  });
+
+  it('falls back to basic attack when golem mana is below actual spell cost', () => {
+    const design = makeDesign('basic', 'earth', 'intermediate', [], ['fireball']);
+    const serialized = makeSerialized(design);
+    const spellDef = SPELLS_DEF['fireball'];
+    // Give golem less mana than the spell costs (fireball costs 2)
+    const golem = makeActiveGolem(design, spellDef.cost.amount - 1, 1.0);
+    // Use 0 armor enemy so basic attack damage is full baseDamage (6)
+    const enemy = makeEnemy({ armor: 0 });
+
+    let damageCount = 0;
+    processGolemAttacks(
+      [golem],
+      { [design.id]: serialized },
+      () => { damageCount++; return { rawMana: 0, elements: {} }; },
+      () => ({ floorHP: 50, floorMaxHP: 100, roomCleared: false }),
+      'fire',
+      () => enemy,
+      () => {},
+    );
+
+    // Should fall back to basic attack since mana is insufficient
+    expect(damageCount).toBeGreaterThan(0);
+  });
+});
+
+// ─── Fix #3: Elemental matchup ───────────────────────────────────────────────
+
+describe('processGolemAttacks - elemental matchup (fix #3)', () => {
+  it('applies super effective elemental bonus (1.5x) to basic attacks', () => {
+    // Water is super effective vs fire (ELEMENT_OPPOSITES['fire'] = 'water')
+    // Use a frame with element that is super effective vs the enemy element
+    // Fire frame (Steel has element 'metal', Crystal has 'crystal')
+    // Let's use computeBasicAttackDamage directly with water element vs fire enemy
+    const dmg = computeBasicAttackDamage(
+      { baseDamage: 10, armorPierce: 0, element: 'water' },
+      0, 0, 'fire',
+    );
+    expect(dmg).toBe(15); // water vs fire = 1.5x
+  });
+
+  it('applies weak elemental bonus (0.75x) when frame element is weak', () => {
+    // Lightning is weak to earth: ELEMENT_OPPOSITES['lightning'] = 'earth'
+    const dmg = computeBasicAttackDamage(
+      { baseDamage: 10, armorPierce: 0, element: 'lightning' },
+      0, 0, 'earth',
+    );
+    expect(dmg).toBe(7.5); // 10 * 0.75
+  });
+
+  it('applies same-element bonus (1.25x) when frame element matches enemy', () => {
+    const dmg = computeBasicAttackDamage(
+      { baseDamage: 10, armorPierce: 0, element: 'fire' },
+      0, 0, 'fire',
+    );
+    expect(dmg).toBe(12.5); // 10 * 1.25
+  });
+
+  it('applies neutral bonus (1.0x) for unrelated elements', () => {
+    // Death element has no specific matchup with fire = neutral
+    const dmg = computeBasicAttackDamage(
+      { baseDamage: 10, armorPierce: 0, element: 'death' },
+      0, 0, 'fire',
+    );
+    expect(dmg).toBe(10); // 1.0x neutral
+  });
+
+  it('applies elemental bonus through processGolemAttacks (integration)', () => {
+    // Crystal frame has element 'crystal'. Test with an enemy element where crystal is neutral.
+    // Crystal vs fire = neutral (1.0x)
+    const design = makeDesign('basic', 'crystal', 'simple');
+    const serialized = makeSerialized(design);
+    const golem = makeActiveGolem(design, undefined, 1.0);
+    const enemy = makeEnemy({ element: 'fire', armor: 0 }); // No armor for clean test
+
+    const frame = FRAMES['crystal'];
+    const expectedDmg = frame.baseDamage; // 1.0x neutral, no armor
+
+    const { capturedDamage } = runGolemAttacks(golem, serialized, design, enemy, 'fire');
+    expect(capturedDamage).toBe(expectedDmg);
+  });
+});
+
+// ─── Fix #4: Enchantment effects ─────────────────────────────────────────────
+
+describe('processGolemAttacks - enchantment effects (fix #4)', () => {
+  it('applies enchantment effects to target enemy on basic attack', () => {
+    const design = makeDesign('basic', 'earth', 'simple', ['sword_fire']);
+    const serialized = makeSerialized(design);
+    const golem = makeActiveGolem(design, undefined, 1.0);
+    const enemy = makeEnemy();
+
+    const appliedEffects: { enemyId: string; effects: { type: string; magnitude: number }[] }[] = [];
+    processGolemAttacks(
+      [golem],
+      { [design.id]: serialized },
+      () => ({ rawMana: 0, elements: {} }),
+      () => ({ floorHP: 50, floorMaxHP: 100, roomCleared: false }),
+      'fire',
+      () => enemy,
+      (enemyId, effects) => { appliedEffects.push({ enemyId, effects }); },
+    );
+
+    expect(appliedEffects.length).toBeGreaterThan(0);
+    expect(appliedEffects[0].effects.some(e => e.type === 'burn')).toBe(true);
+  });
+
+  it('applies multiple enchantment effects when multiple enchantments equipped', () => {
+    const design = makeDesign('basic', 'earth', 'simple', ['sword_fire', 'sword_frost', 'sword_lightning']);
+    const serialized = makeSerialized(design);
+    const golem = makeActiveGolem(design, undefined, 1.0);
+    const enemy = makeEnemy();
+
+    const appliedEffects: { type: string; magnitude: number }[][] = [];
+    processGolemAttacks(
+      [golem],
+      { [design.id]: serialized },
+      () => ({ rawMana: 0, elements: {} }),
+      () => ({ floorHP: 50, floorMaxHP: 100, roomCleared: false }),
+      'fire',
+      () => enemy,
+      (_, effects) => { appliedEffects.push(effects); },
+    );
+
+    const allEffectTypes = appliedEffects.flat().map(e => e.type);
+    expect(allEffectTypes).toContain('burn');
+    expect(allEffectTypes).toContain('slow');
+    expect(allEffectTypes).toContain('shock');
+  });
+
+  it('does not apply enchantment effects when no enchantments equipped', () => {
+    const design = makeDesign('basic', 'earth', 'simple', []);
+    const serialized = makeSerialized(design);
+    const golem = makeActiveGolem(design, undefined, 1.0);
+    const enemy = makeEnemy();
+
+    let effectsCalled = false;
+    processGolemAttacks(
+      [golem],
+      { [design.id]: serialized },
+      () => ({ rawMana: 0, elements: {} }),
+      () => ({ floorHP: 50, floorMaxHP: 100, roomCleared: false }),
+      'fire',
+      () => enemy,
+      () => { effectsCalled = true; },
+    );
+
+    expect(effectsCalled).toBe(false);
+  });
+});
+
+// ─── Fix #5: Armor pierce ────────────────────────────────────────────────────
+
+describe('processGolemAttacks - armor pierce (fix #5)', () => {
+  it('does not multiply damage by (1 + armorPierce)', () => {
+    // Steel frame: baseDamage=18, armorPierce=0.5
+    // Old buggy formula: 18 * (1 + 0.5) = 27
+    // Correct: 18 with 50% armor bypass against 40% armor
+    const design = makeDesign('basic', 'steel', 'simple');
+    const serialized = makeSerialized(design);
+    const golem = makeActiveGolem(design, undefined, 1.0);
+    const enemy = makeEnemy({ armor: 0.4 });
+
+    const frame = FRAMES['steel'];
+    // With 50% armor pierce: effectiveArmor = 0.4 * (1 - 0.5) = 0.2
+    // dmg = 18 * (1 - 0.2) = 14.4
+    const expectedDmg = frame.baseDamage * (1 - 0.4 * (1 - frame.armorPierce));
+
+    const { capturedDamage } = runGolemAttacks(golem, serialized, design, enemy, 'fire');
+
+    // Should NOT be 18 * 1.5 = 27 (old buggy formula)
+    expect(capturedDamage).not.toBe(frame.baseDamage * (1 + frame.armorPierce));
+    // Should be the correct armor-bypassed value
+    expect(capturedDamage).toBe(expectedDmg);
+  });
+
+  it('fully bypasses armor when armorPierce is 1.0', () => {
+    const dmg = computeBasicAttackDamage(
+      { baseDamage: 10, armorPierce: 1.0, element: undefined },
+      0, 0.8, 'fire',
+    );
+    expect(dmg).toBe(10); // Full damage, armor fully bypassed
+  });
+
+  it('applies no armor bypass when armorPierce is 0', () => {
+    const dmg = computeBasicAttackDamage(
+      { baseDamage: 10, armorPierce: 0, element: undefined },
+      0, 0.5, 'fire',
+    );
+    // 50% armor, no pierce: 10 * (1 - 0.5) = 5
+    expect(dmg).toBe(5);
+  });
+
+  it('stacks enchantment armorPierce with frame armorPierce', () => {
+    const framePierce = 0.5;
+    const enchantPierce = 0.15;
+    const totalPierce = Math.min(1, framePierce + enchantPierce);
+
+    const dmg = computeBasicAttackDamage(
+      { baseDamage: 20, armorPierce: framePierce, element: undefined },
+      enchantPierce, 0.4, 'fire',
+    );
+    const expected = 20 * (1 - 0.4 * (1 - totalPierce));
+    expect(dmg).toBe(expected);
+  });
+});
+
+

src/lib/game/stores/golem-combat-actions.ts

@@ -3,14 +3,18 @@
 // All external data is passed in as parameters (no cross-store getState() calls).
 // Implements spec §§10-14: summoning, maintenance, combat, mana, duration.
 
-import { HOURS_PER_TICK } from '../constants';
+import { HOURS_PER_TICK, SPELLS_DEF } from '../constants';
 import { CORES, FRAMES, MIND_CIRCUITS } from '../data/golems';
 import { computeGolemStats, getGolemSlots } from '../data/golems/utils';
+import {
+  resolveEnchantmentEffects,
+  computeBasicAttackDamage,
+} from './golem-combat-helpers';
+import type { GolemEnchantmentEffect } from './golem-combat-helpers';
 import type {
   RuntimeActiveGolem,
   GolemLoadoutEntry,
   EnemyState,
-  ActiveEffect,
 } from '../types';
 
 // ─── Types ───────────────────────────────────────────────────────────────────
@@ -60,22 +64,17 @@ export function summonGolemsOnRoomEntry(
   const newActiveGolems = [...existingActiveGolems];
   const logMessages: string[] = [];
 
-  const activeCount = newActiveGolems.length;
   const baseSlots = getGolemSlots(fabricatorLevel);
   const totalSlots = Math.min(7, baseSlots + disciplineSlotsBonus);
 
   for (const entry of loadout) {
     if (!entry.enabled) continue;
-
-    // Check slot availability (max 7 total per AC-1)
     if (newActiveGolems.length >= totalSlots) {
       logMessages.push('No golem slots available');
       break;
     }
 
     const design = entry.design as SerializedDesign;
-
-    // Resolve components
     const core = CORES[design.coreId];
     const frame = FRAMES[design.frameId];
     const circuit = MIND_CIRCUITS[design.mindCircuitId];
@@ -84,23 +83,20 @@ export function summonGolemsOnRoomEntry(
       continue;
     }
 
-    // Skip if already active
     const alreadyActive = newActiveGolems.some((ag) => ag.designId === entry.designId);
     if (alreadyActive) continue;
 
-    // Build component-based design for cost calculation
     const stats = computeGolemStats({
       id: design.id,
       name: design.name,
       core: { ...core, manaTypes: design.selectedManaTypes.length > 0 ? design.selectedManaTypes : core.manaTypes },
       frame,
       mindCircuit: circuit,
-      enchantments: [], // Simplified — enchantments resolved by ID in full implementation
+      enchantments: [],
       selectedManaTypes: design.selectedManaTypes,
       selectedSpells: design.selectedSpells,
     });
 
-    // Check affordability
     let canAfford = true;
     for (const cost of stats.totalSummonCost) {
       if (cost.type === 'raw') {
@@ -116,7 +112,6 @@ export function summonGolemsOnRoomEntry(
       continue;
     }
 
-    // Deduct summon cost
     for (const cost of stats.totalSummonCost) {
       if (cost.type === 'raw') {
         newRawMana -= cost.amount;
@@ -140,12 +135,7 @@ export function summonGolemsOnRoomEntry(
     logMessages.push(`${entry.design.name} summoned`);
   }
 
-  return {
-    rawMana: newRawMana,
-    elements: newElements,
-    activeGolems: newActiveGolems,
-    logMessages,
-  };
+  return { rawMana: newRawMana, elements: newElements, activeGolems: newActiveGolems, logMessages };
 }
 
 // ─── Maintenance Upkeep (spec §13) ───────────────────────────────────────────
@@ -174,25 +164,17 @@ export function processGolemMaintenance(
   for (const golem of activeGolems) {
     const design = golemDesigns[golem.designId];
     if (!design) continue;
-
     const core = CORES[design.coreId];
     if (!core) continue;
 
-    // Upkeep per tick = (manaRegen × 2) × HOURS_PER_TICK
     const upkeepPerTick = core.manaRegen * 2 * HOURS_PER_TICK;
     const upkeepElement = core.primaryManaType;
-
     const elem = upkeepElement ? newElements[upkeepElement] : null;
 
     if (upkeepElement && elem && elem.unlocked && elem.current >= upkeepPerTick) {
-      // Deduct from element mana
-      newElements[upkeepElement] = {
-        ...elem,
-        current: elem.current - upkeepPerTick,
-      };
+      newElements[upkeepElement] = { ...elem, current: elem.current - upkeepPerTick };
       maintainedGolems.push(golem);
     } else if (!upkeepElement && newRawMana >= upkeepPerTick) {
-      // Deduct from raw mana
       newRawMana -= upkeepPerTick;
       maintainedGolems.push(golem);
     } else if (upkeepElement && (!elem || !elem.unlocked || elem.current < upkeepPerTick)) {
@@ -202,12 +184,7 @@ export function processGolemMaintenance(
     }
   }
 
-  return {
-    rawMana: newRawMana,
-    elements: newElements,
-    maintainedGolems,
-    logMessages,
-  };
+  return { rawMana: newRawMana, elements: newElements, maintainedGolems, logMessages };
 }
 
 // ─── Golem Mana Regen (spec §12) ────────────────────────────────────────────
@@ -222,15 +199,10 @@ export function processGolemManaRegen(
   return activeGolems.map((golem) => {
     const design = golemDesigns[golem.designId];
     if (!design) return golem;
-
     const core = CORES[design.coreId];
     if (!core) return golem;
-
     const manaGain = core.manaRegen * HOURS_PER_TICK;
-    return {
-      ...golem,
-      currentMana: Math.min(core.manaCapacity, golem.currentMana + manaGain),
-    };
+    return { ...golem, currentMana: Math.min(core.manaCapacity, golem.currentMana + manaGain) };
   });
 }
 
@@ -240,6 +212,13 @@ export function processGolemManaRegen(
  * Process golem attacks for one combat tick.
  * Each golem accumulates attackProgress and fires when >= 1.
  * Supports spell casting via Mind Circuit behavior.
+ *
+ * Fixes applied (issue #313):
+ * 1. Spell damage: uses actual SPELLS_DEF[spellId].dmg * frame.magicAffinity
+ * 2. Spell mana cost: uses actual SPELLS_DEF[spellId].cost.amount
+ * 3. Elemental matchup: applies getElementalBonus to basic attacks
+ * 4. Enchantment effects: applies golem enchantment effects on basic attacks
+ * 5. Armor pierce: bypasses enemy armor fraction instead of multiplying damage
  */
 export function processGolemAttacks(
   activeGolems: RuntimeActiveGolem[],
@@ -250,6 +229,9 @@ export function processGolemAttacks(
     modifiedDamage?: number;
   },
   applyDamageToRoom: (dmg: number) => { floorHP: number; floorMaxHP: number; roomCleared: boolean },
+  enemyElement: string,
+  getTargetEnemy: () => EnemyState | null,
+  onApplyEnchantmentEffects: (enemyId: string, effects: GolemEnchantmentEffect[]) => void,
 ): GolemCombatResult {
   let rawMana = 0;
   let elements: Record<string, { current: number; max: number; unlocked: boolean }> = {};
@@ -257,7 +239,6 @@ export function processGolemAttacks(
   let floorMaxHP = 0;
   const logMessages: string[] = [];
   let totalDamageDealt = 0;
-
   const updatedGolems: RuntimeActiveGolem[] = [];
 
   for (const golem of activeGolems) {
@@ -269,6 +250,9 @@ export function processGolemAttacks(
     const circuit = MIND_CIRCUITS[design.mindCircuitId];
     if (!core || !frame || !circuit) continue;
 
+    const enchantmentEffects = resolveEnchantmentEffects(design.enchantmentIds);
+    const bonusArmorPierce = design.enchantmentIds.includes('sword_metal') ? 0.15 : 0;
+
     let attackProgress = golem.attackProgress + HOURS_PER_TICK * frame.attackSpeed;
     const updatedGolem = { ...golem };
     let safetyCounter = 0;
@@ -279,34 +263,47 @@ export function processGolemAttacks(
       if (circuit.spellSlots > 0 && design.selectedSpells.length > 0) {
         const spellIdx = updatedGolem.spellCastIndex % design.selectedSpells.length;
         const spellId = design.selectedSpells[spellIdx];
+        const spellDef = spellId ? SPELLS_DEF[spellId] : null;
 
-        // Spell casting simplified — full implementation needs spell cost/effect lookup
-        if (spellId && updatedGolem.currentMana >= 10) {
-          // Cast spell: damage scaled by magic affinity
-          const spellDmg = 20 * frame.magicAffinity; // Placeholder base spell damage
-          updatedGolem.currentMana -= 10;
-          updatedGolem.spellCastIndex = (updatedGolem.spellCastIndex + 1) % design.selectedSpells.length;
+        if (spellDef) {
+          const spellManaCost = spellDef.cost.amount;
+          if (updatedGolem.currentMana >= spellManaCost) {
+            // FIX #1: Use actual spell damage * magic affinity
+            const spellDmg = spellDef.dmg * frame.magicAffinity;
+            // FIX #2: Deduct actual spell mana cost
+            updatedGolem.currentMana -= spellManaCost;
+            updatedGolem.spellCastIndex = (updatedGolem.spellCastIndex + 1) % design.selectedSpells.length;
 
-          const dmgResult = onDamageDealt(spellDmg);
-          const finalDamage = dmgResult.modifiedDamage || spellDmg;
+            const dmgResult = onDamageDealt(spellDmg);
+            const finalDamage = dmgResult.modifiedDamage || spellDmg;
 
-          if (Number.isFinite(finalDamage)) {
-            const roomResult = applyDamageToRoom(finalDamage);
-            floorHP = roomResult.floorHP;
-            floorMaxHP = roomResult.floorMaxHP;
-            totalDamageDealt += Math.max(0, finalDamage);
-            rawMana = dmgResult.rawMana;
-            elements = dmgResult.elements;
+            if (Number.isFinite(finalDamage)) {
+              const roomResult = applyDamageToRoom(finalDamage);
+              floorHP = roomResult.floorHP;
+              floorMaxHP = roomResult.floorMaxHP;
+              totalDamageDealt += Math.max(0, finalDamage);
+              rawMana = dmgResult.rawMana;
+              elements = dmgResult.elements;
+            }
+
+            attackProgress -= 1;
+            safetyCounter++;
+            continue;
           }
-
-          attackProgress -= 1;
-          safetyCounter++;
-          continue;
         }
       }
 
       // Basic attack
-      let dmg = frame.baseDamage * (1 + frame.armorPierce);
+      // FIX #3, #4, #5: elemental matchup, enchantment effects, proper armor pierce
+      const targetEnemy = getTargetEnemy();
+      const enemyArmor = targetEnemy?.armor ?? 0;
+
+      const dmg = computeBasicAttackDamage(frame, bonusArmorPierce, enemyArmor, enemyElement);
+
+      // Apply enchantment effects to target enemy
+      if (enchantmentEffects.length > 0 && targetEnemy) {
+        onApplyEnchantmentEffects(targetEnemy.id, enchantmentEffects);
+      }
 
       const dmgResult = onDamageDealt(dmg);
       const finalDamage = dmgResult.modifiedDamage || dmg;
@@ -328,13 +325,7 @@ export function processGolemAttacks(
     updatedGolems.push(updatedGolem);
   }
 
-  return {
-    rawMana,
-    elements,
-    activeGolems: updatedGolems,
-    logMessages,
-    totalDamageDealt,
-  };
+  return { rawMana, elements, activeGolems: updatedGolems, logMessages, totalDamageDealt };
 }
 
 // ─── Room Duration Countdown (spec §14) ─────────────────────────────────────
@@ -358,12 +349,10 @@ export function countdownGolemRoomDuration(
   for (const golem of activeGolems) {
     const design = golemDesigns[golem.designId];
     if (!design) continue;
-
     const core = CORES[design.coreId];
     if (!core) continue;
 
     const newRoomsRemaining = golem.roomsRemaining - 1;
-
     if (newRoomsRemaining <= 0) {
       dismissedNames.push(design.name);
       logMessages.push(`${design.name} has faded after ${core.maxRoomDuration} rooms`);

src/lib/game/stores/golem-combat-helpers.test.ts

@@ -0,0 +1,142 @@
+// ─── Golem Combat Helpers Unit Tests (Issue #313) ──────────────────────────────
+// Unit tests for computeBasicAttackDamage and resolveEnchantmentEffects.
+
+import { describe, it, expect } from 'vitest';
+import { computeBasicAttackDamage, resolveEnchantmentEffects } from './golem-combat-helpers';
+
+// ─── computeBasicAttackDamage ────────────────────────────────────────────────
+
+describe('computeBasicAttackDamage', () => {
+  it('returns baseDamage with no armor and no elemental effect', () => {
+    const dmg = computeBasicAttackDamage(
+      { baseDamage: 10, armorPierce: 0, element: undefined },
+      0, 0, 'fire',
+    );
+    expect(dmg).toBe(10);
+  });
+
+  it('applies elemental bonus for super effective matchup', () => {
+    // Water vs Fire = 1.5x (water is opposite of fire)
+    const dmg = computeBasicAttackDamage(
+      { baseDamage: 10, armorPierce: 0, element: 'water' },
+      0, 0, 'fire',
+    );
+    expect(dmg).toBe(15);
+  });
+
+  it('applies elemental penalty for weak matchup', () => {
+    // Lightning vs Earth = 0.75x (lightning is weak to earth)
+    const dmg = computeBasicAttackDamage(
+      { baseDamage: 10, armorPierce: 0, element: 'lightning' },
+      0, 0, 'earth',
+    );
+    expect(dmg).toBe(7.5);
+  });
+
+  it('applies same-element bonus', () => {
+    const dmg = computeBasicAttackDamage(
+      { baseDamage: 10, armorPierce: 0, element: 'fire' },
+      0, 0, 'fire',
+    );
+    expect(dmg).toBe(12.5);
+  });
+
+  it('never returns negative damage', () => {
+    const dmg = computeBasicAttackDamage(
+      { baseDamage: 10, armorPierce: 0, element: undefined },
+      0, 0.99, 'fire',
+    );
+    expect(dmg).toBeGreaterThanOrEqual(0);
+  });
+
+  it('combines elemental bonus and armor pierce', () => {
+    // Water vs Fire = 1.5x, then 50% armor with 25% pierce
+    // effectiveArmor = 0.5 * (1 - 0.25) = 0.375
+    // dmg = 10 * 1.5 * (1 - 0.375) = 9.375
+    const dmg = computeBasicAttackDamage(
+      { baseDamage: 10, armorPierce: 0.25, element: 'water' },
+      0, 0.5, 'fire',
+    );
+    expect(dmg).toBeCloseTo(9.375, 5);
+  });
+
+  it('fully bypasses armor when armorPierce is 1.0', () => {
+    const dmg = computeBasicAttackDamage(
+      { baseDamage: 10, armorPierce: 1.0, element: undefined },
+      0, 0.8, 'fire',
+    );
+    expect(dmg).toBe(10);
+  });
+
+  it('applies no armor bypass when armorPierce is 0', () => {
+    const dmg = computeBasicAttackDamage(
+      { baseDamage: 10, armorPierce: 0, element: undefined },
+      0, 0.5, 'fire',
+    );
+    expect(dmg).toBe(5);
+  });
+
+  it('stacks enchantment armorPierce with frame armorPierce', () => {
+    const totalPierce = Math.min(1, 0.5 + 0.15);
+    const dmg = computeBasicAttackDamage(
+      { baseDamage: 20, armorPierce: 0.5, element: undefined },
+      0.15, 0.4, 'fire',
+    );
+    expect(dmg).toBe(20 * (1 - 0.4 * (1 - totalPierce)));
+  });
+});
+
+// ─── resolveEnchantmentEffects ────────────────────────────────────────────────
+
+describe('resolveEnchantmentEffects', () => {
+  it('resolves sword_fire to burn effect', () => {
+    const effects = resolveEnchantmentEffects(['sword_fire']);
+    expect(effects).toHaveLength(1);
+    expect(effects[0].type).toBe('burn');
+    expect(effects[0].magnitude).toBe(3);
+  });
+
+  it('resolves sword_frost to slow effect', () => {
+    const effects = resolveEnchantmentEffects(['sword_frost']);
+    expect(effects).toHaveLength(1);
+    expect(effects[0].type).toBe('slow');
+  });
+
+  it('resolves sword_metal to armorPierce effect', () => {
+    const effects = resolveEnchantmentEffects(['sword_metal']);
+    expect(effects).toHaveLength(1);
+    expect(effects[0].type).toBe('armorPierce');
+    expect(effects[0].magnitude).toBe(0.15);
+  });
+
+  it('resolves sword_lightning to shock effect', () => {
+    const effects = resolveEnchantmentEffects(['sword_lightning']);
+    expect(effects).toHaveLength(1);
+    expect(effects[0].type).toBe('shock');
+  });
+
+  it('resolves sword_shadow to weaken effect', () => {
+    const effects = resolveEnchantmentEffects(['sword_shadow']);
+    expect(effects).toHaveLength(1);
+    expect(effects[0].type).toBe('weaken');
+  });
+
+  it('returns empty array for unknown enchantment IDs', () => {
+    const effects = resolveEnchantmentEffects(['nonexistent_enchant']);
+    expect(effects).toHaveLength(0);
+  });
+
+  it('resolves multiple enchantments', () => {
+    const effects = resolveEnchantmentEffects(['sword_fire', 'sword_lightning', 'sword_shadow']);
+    expect(effects).toHaveLength(3);
+    const types = effects.map(e => e.type);
+    expect(types).toContain('burn');
+    expect(types).toContain('shock');
+    expect(types).toContain('weaken');
+  });
+
+  it('handles empty array', () => {
+    const effects = resolveEnchantmentEffects([]);
+    expect(effects).toHaveLength(0);
+  });
+});

src/lib/game/stores/golem-combat-helpers.ts

@@ -0,0 +1,133 @@
+// ─── Golem Combat Helpers ─────────────────────────────────────────────────────
+// Shared helpers for golem combat: enchantment resolution, basic attack damage,
+// and store-wrapper for processGolemAttacks.
+// Extracted from golem-combat-actions.ts to stay under the 400-line file limit.
+
+import { GOLEM_ENCHANTMENTS } from '../data/golems';
+import { getElementalBonus } from '../utils';
+import type { CombatStore, CombatState } from './combat-state.types';
+import type {
+  ActiveEffect,
+  EnemyState,
+  RuntimeActiveGolem,
+} from '../types';
+
+// ─── Enchantment Effect Types ────────────────────────────────────────────────
+
+export interface GolemEnchantmentEffect {
+  type: 'burn' | 'slow' | 'shock' | 'weaken' | 'armorPierce' | 'criticalChance' | 'soak' | 'shieldBreak';
+  magnitude: number;
+}
+
+// ─── Enchantment Resolution ──────────────────────────────────────────────────
+
+/** Resolve enchantment effects from a list of enchantment IDs. */
+export function resolveEnchantmentEffects(enchantmentIds: string[]): GolemEnchantmentEffect[] {
+  const effects: GolemEnchantmentEffect[] = [];
+  for (const id of enchantmentIds) {
+    const ench = GOLEM_ENCHANTMENTS[id];
+    if (!ench) continue;
+    switch (ench.effect) {
+      case 'burn': effects.push({ type: 'burn', magnitude: 3 }); break;
+      case 'slow': effects.push({ type: 'slow', magnitude: 0.3 }); break;
+      case 'shock': effects.push({ type: 'shock', magnitude: 0.25 }); break;
+      case 'weaken': effects.push({ type: 'weaken', magnitude: 0.2 }); break;
+      case 'armorPierce': effects.push({ type: 'armorPierce', magnitude: 0.15 }); break;
+      case 'criticalChance': effects.push({ type: 'criticalChance', magnitude: 0.1 }); break;
+      case 'soak': effects.push({ type: 'soak', magnitude: 0.3 }); break;
+      case 'shieldBreak': effects.push({ type: 'shieldBreak', magnitude: 0.25 }); break;
+    }
+  }
+  return effects;
+}
+
+// ─── Basic Attack Damage ─────────────────────────────────────────────────────
+
+/**
+ * Compute basic attack damage for a golem.
+ * Applies elemental matchup bonus and proper armor pierce (bypasses armor fraction).
+ */
+export function computeBasicAttackDamage(
+  frame: { baseDamage: number; armorPierce: number; element?: string },
+  enchantmentBonusArmorPierce: number,
+  enemyArmor: number,
+  enemyElement: string,
+): number {
+  let dmg = frame.baseDamage;
+  if (frame.element) {
+    dmg *= getElementalBonus(frame.element, enemyElement);
+  }
+  const totalArmorPierce = Math.min(1, frame.armorPierce + enchantmentBonusArmorPierce);
+  const effectiveArmor = enemyArmor * (1 - totalArmorPierce);
+  if (effectiveArmor > 0) {
+    dmg *= (1 - effectiveArmor);
+  }
+  return Math.max(0, dmg);
+}
+
+// ─── Golem Attacks Store Wrapper ─────────────────────────────────────────────
+
+// Import here is safe: only used inside the function body, not at module init time.
+import { processGolemAttacks } from './golem-combat-actions'; // eslint-disable-line
+import type { GolemCombatResult } from './golem-combat-actions';
+
+interface SerializedDesign {
+  id: string;
+  name: string;
+  coreId: string;
+  frameId: string;
+  mindCircuitId: string;
+  enchantmentIds: string[];
+  selectedManaTypes: string[];
+  selectedSpells: string[];
+}
+
+/** Convenience wrapper that wires up processGolemAttacks with store callbacks. */
+export function processGolemAttacksFromStore(
+  activeGolems: RuntimeActiveGolem[],
+  golemDesigns: Record<string, SerializedDesign>,
+  onDamageDealt: (damage: number) => {
+    rawMana: number;
+    elements: Record<string, { current: number; max: number; unlocked: boolean }>;
+    modifiedDamage?: number;
+  },
+  golemApplyDamageToRoom: (dmg: number) => { floorHP: number; floorMaxHP: number; roomCleared: boolean },
+  enemyElement: string,
+  get: () => CombatStore,
+  set: (s: Partial<CombatState>) => void,
+): GolemCombatResult {
+  return processGolemAttacks(
+    activeGolems,
+    golemDesigns,
+    onDamageDealt,
+    golemApplyDamageToRoom,
+    enemyElement,
+    () => {
+      const room = get().currentRoom;
+      const living = room.enemies.filter((e) => e.hp > 0);
+      if (living.length === 0) return null;
+      return living.reduce((lowest, e) => (e.hp < lowest.hp ? e : lowest));
+    },
+    (enemyId, effects) => {
+      const room = get().currentRoom;
+      const updatedEnemies = room.enemies.map((e) => {
+        if (e.id !== enemyId) return e;
+        const newEffects = [...e.activeEffects];
+        for (const effect of effects) {
+          const idx = newEffects.findIndex((ae) => ae.type === effect.type);
+          if (idx >= 0) {
+            newEffects[idx] = {
+              ...newEffects[idx],
+              remainingDuration: 4,
+              magnitude: Math.max(newEffects[idx].magnitude, effect.magnitude),
+            };
+          } else {
+            newEffects.push({ type: effect.type, remainingDuration: 4, magnitude: effect.magnitude, source: 'golem' });
+          }
+        }
+        return { ...e, activeEffects: newEffects };
+      });
+      set({ currentRoom: { ...room, enemies: updatedEnemies } });
+    },
+  );
+}