Add a basic perk system

The perks aren't visible yet. There's only one perk: Ravenous,
which makes the dire wolf even better at eating you.

src/game/combat.ts

@@ -3,6 +3,7 @@ import { TextLike, DynText, ToBe, LiveText, PairLineArgs, PairLine } from './lan
 import { LogEntry, LogLines, FAElem, LogLine, FormatEntry, FormatOpt, PropElem, nilLog, Newline } from './interface'
 import { Resistances } from './entity'
 import { World } from './world'
+import { TestCategory } from './combat/tests'
 
 export enum DamageType {
   Pierce = "Pierce",
@@ -555,6 +556,20 @@ export class Effective {
   scale (scale: number): number {
     return scale
   }
+
+  /**
+   * Additively modifies a creature's score for an offensive test
+   */
+  modTestOffense (attacker: Creature, defender: Creature, kind: TestCategory): number {
+    return 0
+  }
+
+  /**
+   * Additively modifies a creature's score for a defensive test
+   */
+  modTestDefense (defender: Creature, attacker: Creature, kind: TestCategory): number {
+    return 0
+  }
 }
 /**
  * A displayable status effect

src/game/combat/perks.ts

@@ -0,0 +1,27 @@
+import { Effective } from '../combat'
+import { TextLike } from '../language'
+import { Creature } from '../creature'
+import { TestCategory } from './tests'
+
+export abstract class Perk extends Effective {
+  constructor (name: TextLike, desc: TextLike) {
+    super()
+  }
+}
+
+export class RavenousPerk extends Perk {
+  constructor () {
+    super(
+      "Ravenous",
+      "+10 to your score when eating someone if you have no prey in you."
+    )
+  }
+
+  modTestOffense (user: Creature, target: Creature, kind: TestCategory): number {
+    if (user.voreStats["Prey Count"] === 0 && kind === TestCategory.Vore) {
+      return 10
+    } else {
+      return 0
+    }
+  }
+}

src/game/combat/tests.ts

@@ -60,8 +60,8 @@ export class OpposedStatTest extends RandomTest {
   }
 
   odds (user: Creature, target: Creature): number {
-    const userScore = this.getScore(user, this.userStats)
-    const targetScore = this.getScore(target, this.targetStats)
+    const userScore = this.getScore(user, this.userStats) + user.effects.reduce((total, effect) => total + effect.modTestOffense(user, target, this.category), 0)
+    const targetScore = this.getScore(target, this.targetStats) + target.effects.reduce((total, effect) => total + effect.modTestDefense(target, user, this.category), 0)
 
     return this.f(userScore - targetScore + this.bias)
   }

src/game/creature.ts

@@ -6,6 +6,7 @@ import { Item, EquipmentSlot, Equipment, ItemKind, Currency } from './items'
 import { PassAction } from './combat/actions'
 import { AI } from './ai'
 import { Mortal } from './entity'
+import { Perk } from './combat/perks'
 
 export class Creature extends Mortal {
   containers: Array<VoreContainer> = []
@@ -22,11 +23,14 @@ export class Creature extends Mortal {
     return (this.statusEffects as Effective[]).concat(
       Object.values(this.equipment).filter(item => item !== undefined).flatMap(
         item => (item as Equipment).effects
-      )
+      ),
+      this.perks
     )
   }
 
   statusEffects: Array<StatusEffect> = [];
+  perks: Array<Perk> = [];
+
   groupActions: Array<GroupAction> = [];
   items: Array<Item> = [];
   /* eslint-disable-next-line */

src/game/creatures/wolves.ts

@@ -4,6 +4,7 @@ import { MalePronouns, ImproperNoun, FemalePronouns, TheyPronouns, Verb } from '
 import { Stomach, Bowels, anyVore } from '../vore'
 import { AttackAction, TransferAction } from '../combat/actions'
 import { VoreAI } from '../ai'
+import { RavenousPerk } from '../combat/perks'
 
 export class Wolf extends Creature {
   constructor () {
@@ -54,6 +55,8 @@ export class DireWolf extends Creature {
     this.side = Side.Monsters
     this.ai = new VoreAI()
 
+    this.perks.push(new RavenousPerk())
+
     this.actions.push(
       new AttackAction(
         new StatDamageFormula([