Allow stat tests to be biased

src/game/combat/actions.ts

@@ -33,7 +33,7 @@ export abstract class DamageAction extends Action {
       desc,
       [new CapableCondition(), new EnemyCondition()].concat(conditions)
     )
-    this.test = new StatTest(Stat.Power)
+    this.test = new StatTest(Stat.Power, 10)
   }
 
   execute (user: Creature, target: Creature): LogEntry {

src/game/combat/tests.ts

@@ -30,10 +30,11 @@ abstract class RandomTest implements CombatTest {
 
 export class StatVigorTest extends RandomTest {
   private f: (x: number) => number
+  private k = 0.1
 
-  constructor (public readonly stat: Stat, k = 0.1) {
+  constructor (public readonly stat: Stat, private bias = 0) {
     super()
-    this.f = logistic(0, 1, k)
+    this.f = logistic(0, 1, this.k)
   }
 
   odds (user: Creature, target: Creature): number {
@@ -56,7 +57,7 @@ export class StatVigorTest extends RandomTest {
       userPercent *= 4
     }
 
-    return this.f(user.stats[this.stat] * userPercent - target.stats[this.stat] * targetPercent)
+    return this.f(this.bias + user.stats[this.stat] * userPercent - target.stats[this.stat] * targetPercent)
   }
 
   explain (user: Creature, target: Creature): LogEntry {
@@ -82,7 +83,7 @@ export class StatVigorTest extends RandomTest {
     }
     const userMod = user.stats[this.stat] * userPercent
     const targetMod = target.stats[this.stat] * targetPercent
-    const delta = (userMod - targetMod)
+    const delta = userMod - targetMod
 
     if (delta === 0) {
       result = new LogLine('You and the target have the same effective', new PropElem(this.stat), '.')
@@ -100,14 +101,15 @@ export class StatVigorTest extends RandomTest {
 
 export class StatTest extends RandomTest {
   private f: (x: number) => number
+  private k = 0.1
 
-  constructor (public readonly stat: Stat, k = 0.1) {
+  constructor (public readonly stat: Stat, private bias = 0) {
     super()
-    this.f = logistic(0, 1, k)
+    this.f = logistic(0, 1, this.k)
   }
 
   odds (user: Creature, target: Creature): number {
-    return this.f(user.stats[this.stat] - target.stats[this.stat])
+    return this.f(this.bias + user.stats[this.stat] - target.stats[this.stat])
   }
 
   explain (user: Creature, target: Creature): LogEntry {