diff --git a/src/battle-scene.ts b/src/battle-scene.ts
index 19f8dad862e..71f4dc7b9f6 100644
--- a/src/battle-scene.ts
+++ b/src/battle-scene.ts
@@ -230,7 +230,7 @@ export default class BattleScene extends SceneBase {
   private fieldOverlay: Phaser.GameObjects.Rectangle;
   private shopOverlay: Phaser.GameObjects.Rectangle;
   private shopOverlayShown: boolean = false;
-  private shopOverlayOpacity: number = .80;
+  private shopOverlayOpacity: number = .8;
 
   public modifiers: PersistentModifier[];
   private enemyModifiers: PersistentModifier[];
@@ -1056,7 +1056,7 @@ export default class BattleScene extends SceneBase {
           playerField.forEach(p => applyAbAttrs(DoubleBattleChanceAbAttr, p, null, doubleChance));
           doubleTrainer = !Utils.randSeedInt(doubleChance.value);
           // Add a check that special trainers can't be double except for tate and liza - they should use the normal double chance
-          if (trainerConfigs[trainerType].trainerTypeDouble && !(trainerType === TrainerType.TATE || trainerType === TrainerType.LIZA)) {
+          if (trainerConfigs[trainerType].trainerTypeDouble && ![ TrainerType.TATE, TrainerType.LIZA ].includes(trainerType)) {
             doubleTrainer = false;
           }
         }
diff --git a/src/battle.ts b/src/battle.ts
index b8df7635472..b6ae5354e5a 100644
--- a/src/battle.ts
+++ b/src/battle.ts
@@ -294,7 +294,7 @@ export default class Battle {
           if (pokemon.species.speciesId === Species.TAPU_KOKO || pokemon.species.speciesId === Species.TAPU_LELE || pokemon.species.speciesId === Species.TAPU_BULU || pokemon.species.speciesId === Species.TAPU_FINI) {
             return "battle_legendary_tapu";
           }
-          if (pokemon.species.speciesId === Species.COSMOG || pokemon.species.speciesId === Species.COSMOEM || pokemon.species.speciesId === Species.SOLGALEO || pokemon.species.speciesId === Species.LUNALA) {
+          if ([ Species.COSMOG, Species.COSMOEM, Species.SOLGALEO, Species.LUNALA ].includes(pokemon.species.speciesId)) {
             return "battle_legendary_sol_lun";
           }
           if (pokemon.species.speciesId === Species.NECROZMA) {
@@ -308,7 +308,7 @@ export default class Battle {
               return "battle_legendary_ultra_nec";
             }
           }
-          if (pokemon.species.speciesId === Species.NIHILEGO || pokemon.species.speciesId === Species.BUZZWOLE || pokemon.species.speciesId === Species.PHEROMOSA || pokemon.species.speciesId === Species.XURKITREE || pokemon.species.speciesId === Species.CELESTEELA || pokemon.species.speciesId === Species.KARTANA || pokemon.species.speciesId === Species.GUZZLORD || pokemon.species.speciesId === Species.POIPOLE || pokemon.species.speciesId === Species.NAGANADEL || pokemon.species.speciesId === Species.STAKATAKA || pokemon.species.speciesId === Species.BLACEPHALON) {
+          if ([ Species.NIHILEGO, Species.BUZZWOLE, Species.PHEROMOSA, Species.XURKITREE, Species.CELESTEELA, Species.KARTANA, Species.GUZZLORD, Species.POIPOLE, Species.NAGANADEL, Species.STAKATAKA, Species.BLACEPHALON ].includes(pokemon.species.speciesId)) {
             return "battle_legendary_ub";
           }
           if (pokemon.species.speciesId === Species.ZACIAN || pokemon.species.speciesId === Species.ZAMAZENTA) {
diff --git a/src/data/ability.ts b/src/data/ability.ts
index 40461f72e97..af97151f4b0 100644
--- a/src/data/ability.ts
+++ b/src/data/ability.ts
@@ -286,7 +286,7 @@ export class BlockItemTheftAbAttr extends AbAttr {
   getTriggerMessage(pokemon: Pokemon, abilityName: string, ...args: any[]) {
     return i18next.t("abilityTriggers:blockItemTheft", {
       pokemonNameWithAffix: getPokemonNameWithAffix(pokemon),
-      abilityName: abilityName,
+      abilityName
     });
   }
 }
@@ -405,7 +405,7 @@ export class TypeImmunityHealAbAttr extends TypeImmunityAbAttr {
         if (!simulated) {
           const abilityName = (!passive ? pokemon.getAbility() : pokemon.getPassiveAbility()).name;
           pokemon.scene.unshiftPhase(new PokemonHealPhase(pokemon.scene, pokemon.getBattlerIndex(),
-            Math.max(Math.floor(pokemon.getMaxHp() / 4), 1), i18next.t("abilityTriggers:typeImmunityHeal", {pokemonNameWithAffix: getPokemonNameWithAffix(pokemon), abilityName: abilityName}), true));
+            Math.max(Math.floor(pokemon.getMaxHp() / 4), 1), i18next.t("abilityTriggers:typeImmunityHeal", { pokemonNameWithAffix: getPokemonNameWithAffix(pokemon), abilityName }), true));
         }
       }
       return true;
@@ -485,7 +485,7 @@ export class NonSuperEffectiveImmunityAbAttr extends TypeImmunityAbAttr {
   getTriggerMessage(pokemon: Pokemon, abilityName: string, ...args: any[]): string {
     return i18next.t("abilityTriggers:nonSuperEffectiveImmunity", {
       pokemonNameWithAffix: getPokemonNameWithAffix(pokemon),
-      abilityName: abilityName,
+      abilityName
     });
   }
 }
@@ -777,7 +777,7 @@ export class PostDefendTypeChangeAbAttr extends PostDefendAbAttr {
   getTriggerMessage(pokemon: Pokemon, abilityName: string, ...args: any[]): string {
     return i18next.t("abilityTriggers:postDefendTypeChange", {
       pokemonNameWithAffix: getPokemonNameWithAffix(pokemon),
-      abilityName: abilityName,
+      abilityName,
       typeName: i18next.t(`pokemonInfo:Type.${Type[pokemon.getTypes(true)[0]]}`)
     });
   }
@@ -901,7 +901,7 @@ export class PostDefendContactDamageAbAttr extends PostDefendAbAttr {
   getTriggerMessage(pokemon: Pokemon, abilityName: string, ...args: any[]): string {
     return i18next.t("abilityTriggers:postDefendContactDamage", {
       pokemonNameWithAffix: getPokemonNameWithAffix(pokemon),
-      abilityName: abilityName,
+      abilityName
     });
   }
 }
@@ -999,7 +999,7 @@ export class PostDefendAbilityGiveAbAttr extends PostDefendAbAttr {
   getTriggerMessage(pokemon: Pokemon, abilityName: string, ...args: any[]): string {
     return i18next.t("abilityTriggers:postDefendAbilityGive", {
       pokemonNameWithAffix: getPokemonNameWithAffix(pokemon),
-      abilityName: abilityName,
+      abilityName
     });
   }
 }
@@ -1083,9 +1083,8 @@ export class MoveEffectChanceMultiplierAbAttr extends AbAttr {
    *             [1]: {@linkcode Moves } Move used by the ability user.
    */
   apply(pokemon: Pokemon, passive: boolean, cancelled: Utils.BooleanHolder, args: any[]): boolean {
-    //Disable showAbility during getTargetBenefitScore
-    const showAbility = args[4];
-    this.showAbility = showAbility;
+    // Disable showAbility during getTargetBenefitScore
+    this.showAbility = args[4];
     if ((args[0] as Utils.NumberHolder).value <= 0 || (args[1] as Move).id === Moves.ORDER_UP) {
       return false;
     }
@@ -1797,7 +1796,7 @@ export class IntimidateImmunityAbAttr extends AbAttr {
   getTriggerMessage(pokemon: Pokemon, abilityName: string, ...args: any[]): string {
     return i18next.t("abilityTriggers:intimidateImmunity", {
       pokemonNameWithAffix: getPokemonNameWithAffix(pokemon),
-      abilityName: abilityName,
+      abilityName
     });
   }
 }
@@ -2354,8 +2353,8 @@ export class ProtectStatAbAttr extends PreStatChangeAbAttr {
   getTriggerMessage(pokemon: Pokemon, abilityName: string, ...args: any[]): string {
     return i18next.t("abilityTriggers:protectStat", {
       pokemonNameWithAffix: getPokemonNameWithAffix(pokemon),
-      abilityName: abilityName,
-      statName: this.protectedStat !== undefined ? getBattleStatName(this.protectedStat) : "stats", // TODO : Change "stats" to i18next.t("battle:stats") after PR#2600 merged to 'main'
+      abilityName,
+      statName: this.protectedStat !== undefined ? getBattleStatName(this.protectedStat) : i18next.t("battle:stats")
     });
   }
 }
@@ -2421,12 +2420,12 @@ export class StatusEffectImmunityAbAttr extends PreSetStatusAbAttr {
     return this.immuneEffects.length ?
       i18next.t("abilityTriggers:statusEffectImmunityWithName", {
         pokemonNameWithAffix: getPokemonNameWithAffix(pokemon),
-        abilityName: abilityName,
+        abilityName,
         statusEffectName: getStatusEffectDescriptor(args[0] as StatusEffect)
       }) :
       i18next.t("abilityTriggers:statusEffectImmunity", {
         pokemonNameWithAffix: getPokemonNameWithAffix(pokemon),
-        abilityName: abilityName,
+        abilityName
       });
   }
 }
@@ -2458,7 +2457,7 @@ export class BattlerTagImmunityAbAttr extends PreApplyBattlerTagAbAttr {
   getTriggerMessage(pokemon: Pokemon, abilityName: string, ...args: any[]): string {
     return i18next.t("abilityTriggers:battlerTagImmunity", {
       pokemonNameWithAffix: getPokemonNameWithAffix(pokemon),
-      abilityName: abilityName,
+      abilityName,
       battlerTagName: (args[0] as BattlerTag).getDescriptor()
     });
   }
@@ -2844,7 +2843,7 @@ export class PostWeatherLapseHealAbAttr extends PostWeatherLapseAbAttr {
       const scene = pokemon.scene;
       const abilityName = (!passive ? pokemon.getAbility() : pokemon.getPassiveAbility()).name;
       scene.unshiftPhase(new PokemonHealPhase(scene, pokemon.getBattlerIndex(),
-        Math.max(Math.floor(pokemon.getMaxHp() / (16 / this.healFactor)), 1), i18next.t("abilityTriggers:postWeatherLapseHeal", { pokemonNameWithAffix: getPokemonNameWithAffix(pokemon), abilityName: abilityName }), true));
+        Math.max(Math.floor(pokemon.getMaxHp() / (16 / this.healFactor)), 1), i18next.t("abilityTriggers:postWeatherLapseHeal", { pokemonNameWithAffix: getPokemonNameWithAffix(pokemon), abilityName }), true));
       return true;
     }
 
@@ -2864,7 +2863,7 @@ export class PostWeatherLapseDamageAbAttr extends PostWeatherLapseAbAttr {
   applyPostWeatherLapse(pokemon: Pokemon, passive: boolean, weather: Weather, args: any[]): boolean {
     const scene = pokemon.scene;
     const abilityName = (!passive ? pokemon.getAbility() : pokemon.getPassiveAbility()).name;
-    scene.queueMessage(i18next.t("abilityTriggers:postWeatherLapseDamage", { pokemonNameWithAffix: getPokemonNameWithAffix(pokemon), abilityName: abilityName }));
+    scene.queueMessage(i18next.t("abilityTriggers:postWeatherLapseDamage", { pokemonNameWithAffix: getPokemonNameWithAffix(pokemon), abilityName }));
     pokemon.damageAndUpdate(Math.ceil(pokemon.getMaxHp() / (16 / this.damageFactor)), HitResult.OTHER);
     return true;
   }
@@ -2938,7 +2937,7 @@ export class PostTurnStatusHealAbAttr extends PostTurnAbAttr {
         const scene = pokemon.scene;
         const abilityName = (!passive ? pokemon.getAbility() : pokemon.getPassiveAbility()).name;
         scene.unshiftPhase(new PokemonHealPhase(scene, pokemon.getBattlerIndex(),
-          Math.max(Math.floor(pokemon.getMaxHp() / 8), 1), i18next.t("abilityTriggers:poisonHeal", { pokemonName: getPokemonNameWithAffix(pokemon), abilityName: abilityName}), true));
+          Math.max(Math.floor(pokemon.getMaxHp() / 8), 1), i18next.t("abilityTriggers:poisonHeal", { pokemonName: getPokemonNameWithAffix(pokemon), abilityName }), true));
         return true;
       }
     }
@@ -3031,10 +3030,11 @@ export class PostTurnLootAbAttr extends PostTurnAbAttr {
     ) as BerryModifier | undefined;
 
     if (!berryModifier) {
+      const newBerry = new BerryModifier(chosenBerry, pokemon.id, chosenBerryType, 1);
       if (pokemon.isPlayer()) {
-        pokemon.scene.addModifier(new BerryModifier(chosenBerry, pokemon.id, chosenBerryType, 1));
+        pokemon.scene.addModifier(newBerry);
       } else {
-        pokemon.scene.addEnemyModifier(new BerryModifier(chosenBerry, pokemon.id, chosenBerryType, 1));
+        pokemon.scene.addEnemyModifier(newBerry);
       }
     } else if (berryModifier.stackCount < berryModifier.getMaxHeldItemCount(pokemon)) {
       berryModifier.stackCount++;
@@ -3095,7 +3095,7 @@ export class PostTurnHealAbAttr extends PostTurnAbAttr {
       const scene = pokemon.scene;
       const abilityName = (!passive ? pokemon.getAbility() : pokemon.getPassiveAbility()).name;
       scene.unshiftPhase(new PokemonHealPhase(scene, pokemon.getBattlerIndex(),
-        Math.max(Math.floor(pokemon.getMaxHp() / 16), 1), i18next.t("abilityTriggers:postTurnHeal", { pokemonNameWithAffix: getPokemonNameWithAffix(pokemon), abilityName: abilityName }), true));
+        Math.max(Math.floor(pokemon.getMaxHp() / 16), 1), i18next.t("abilityTriggers:postTurnHeal", { pokemonNameWithAffix: getPokemonNameWithAffix(pokemon), abilityName }), true));
       return true;
     }
 
@@ -3347,7 +3347,7 @@ export class HealFromBerryUseAbAttr extends AbAttr {
         pokemon.scene,
         pokemon.getBattlerIndex(),
         Math.max(Math.floor(pokemon.getMaxHp() * this.healPercent), 1),
-        i18next.t("abilityTriggers:healFromBerryUse", { pokemonNameWithAffix: getPokemonNameWithAffix(pokemon), abilityName: abilityName }),
+        i18next.t("abilityTriggers:healFromBerryUse", { pokemonNameWithAffix: getPokemonNameWithAffix(pokemon), abilityName }),
         true
       )
     );
@@ -3422,7 +3422,7 @@ export class ArenaTrapAbAttr extends CheckTrappedAbAttr {
   }
 
   getTriggerMessage(pokemon: Pokemon, abilityName: string, ...args: any[]): string {
-    return i18next.t("abilityTriggers:arenaTrap", { pokemonNameWithAffix: getPokemonNameWithAffix(pokemon), abilityName: abilityName });
+    return i18next.t("abilityTriggers:arenaTrap", { pokemonNameWithAffix: getPokemonNameWithAffix(pokemon), abilityName });
   }
 }
 
@@ -3540,7 +3540,7 @@ export class PostFaintContactDamageAbAttr extends PostFaintAbAttr {
   }
 
   getTriggerMessage(pokemon: Pokemon, abilityName: string, ...args: any[]): string {
-    return i18next.t("abilityTriggers:postFaintContactDamage", { pokemonNameWithAffix: getPokemonNameWithAffix(pokemon), abilityName: abilityName });
+    return i18next.t("abilityTriggers:postFaintContactDamage", { pokemonNameWithAffix: getPokemonNameWithAffix(pokemon), abilityName });
   }
 }
 
@@ -3560,7 +3560,7 @@ export class PostFaintHPDamageAbAttr extends PostFaintAbAttr {
   }
 
   getTriggerMessage(pokemon: Pokemon, abilityName: string, ...args: any[]): string {
-    return i18next.t("abilityTriggers:postFaintHpDamage", { pokemonNameWithAffix: getPokemonNameWithAffix(pokemon), abilityName: abilityName });
+    return i18next.t("abilityTriggers:postFaintHpDamage", { pokemonNameWithAffix: getPokemonNameWithAffix(pokemon), abilityName });
   }
 }
 
@@ -3918,7 +3918,7 @@ export class IceFaceBlockPhysicalAbAttr extends ReceivedMoveDamageMultiplierAbAt
    * @returns {string} - The trigger message.
    */
   getTriggerMessage(pokemon: Pokemon, abilityName: string, ...args: any[]): string {
-    return i18next.t("abilityTriggers:iceFaceAvoidedDamage", { pokemonName: getPokemonNameWithAffix(pokemon), abilityName: abilityName });
+    return i18next.t("abilityTriggers:iceFaceAvoidedDamage", { pokemonName: getPokemonNameWithAffix(pokemon), abilityName });
   }
 }
 
@@ -3993,7 +3993,7 @@ async function applyAbAttrsInternal<TAttr extends AbAttr>(
       pokemon.scene.setPhaseQueueSplice();
 
       let result = applyFunc(attr, passive);
-      // TODO Remove this when promises get reworked PR#924
+      // TODO Remove this when promises get reworked
       if (result instanceof Promise) {
         result = await result;
       }
diff --git a/src/data/battle-stat.ts b/src/data/battle-stat.ts
index 47f52b46d94..d70e6655f8c 100644
--- a/src/data/battle-stat.ts
+++ b/src/data/battle-stat.ts
@@ -1,4 +1,4 @@
-import i18next, {ParseKeys} from "i18next";
+import i18next, { ParseKeys } from "i18next";
 
 export enum BattleStat {
   ATK,
@@ -32,7 +32,7 @@ export function getBattleStatName(stat: BattleStat) {
   }
 }
 
-export function getBattleStatLevelChangeDescription(pokemonNameWithAffix: string, stats: string, levels: integer, up: boolean, count: integer = 1) {
+export function getBattleStatLevelChangeDescription(pokemonNameWithAffix: string, stats: string, levels: integer, up: boolean, count: number = 1) {
   const stringKey = (() => {
     if (up) {
       switch (levels) {
diff --git a/src/data/battler-tags.ts b/src/data/battler-tags.ts
index 2755fd0bbbe..97c42fed514 100644
--- a/src/data/battler-tags.ts
+++ b/src/data/battler-tags.ts
@@ -31,14 +31,14 @@ export enum BattlerTagLapseType {
 
 export class BattlerTag {
   public tagType: BattlerTagType;
-  public lapseType: BattlerTagLapseType[];
+  public lapseTypes: BattlerTagLapseType[];
   public turnCount: number;
   public sourceMove: Moves;
   public sourceId?: number;
 
   constructor(tagType: BattlerTagType, lapseType: BattlerTagLapseType | BattlerTagLapseType[], turnCount: number, sourceMove: Moves, sourceId?: number) {
     this.tagType = tagType;
-    this.lapseType = typeof lapseType === "number" ? [ lapseType ] : lapseType;
+    this.lapseTypes = Array.isArray(lapseType) ? lapseType : [ lapseType ];
     this.turnCount = turnCount;
     this.sourceMove = sourceMove;
     this.sourceId = sourceId;
@@ -650,8 +650,7 @@ export class OctolockTag extends TrappedTag {
   }
 
   canAdd(pokemon: Pokemon): boolean {
-    const isOctolocked = pokemon.getTag(BattlerTagType.OCTOLOCK);
-    return !isOctolocked;
+    return !pokemon.getTag(BattlerTagType.OCTOLOCK);
   }
 
   lapse(pokemon: Pokemon, lapseType: BattlerTagLapseType): boolean {
@@ -1628,8 +1627,8 @@ export class StockpilingTag extends BattlerTag {
     super.loadTag(source);
     this.stockpiledCount = source.stockpiledCount || 0;
     this.statChangeCounts = {
-      [BattleStat.DEF]: source.statChangeCounts?.[BattleStat.DEF] || 0,
-      [BattleStat.SPDEF]: source.statChangeCounts?.[BattleStat.SPDEF] || 0,
+      [ BattleStat.DEF ]: source.statChangeCounts?.[ BattleStat.DEF ] ?? 0,
+      [ BattleStat.SPDEF ]: source.statChangeCounts?.[ BattleStat.SPDEF ] ?? 0,
     };
   }
 
diff --git a/src/data/challenge.ts b/src/data/challenge.ts
index ad8c312bdf6..701183e1733 100644
--- a/src/data/challenge.ts
+++ b/src/data/challenge.ts
@@ -17,6 +17,9 @@ import { Gender } from "./gender";
 import { pokemonEvolutions } from "./pokemon-evolutions";
 import { pokemonFormChanges } from "./pokemon-forms";
 
+/** A constant for the default max cost of the starting party before a run */
+const DEFAULT_PARTY_MAX_COST = 10;
+
 /**
  * An enum for all the challenge types. The parameter entries on these describe the
  * parameters to use when calling the applyChallenges function.
@@ -689,11 +692,11 @@ export class LowerStarterMaxCostChallenge extends Challenge {
     if (overrideValue === undefined) {
       overrideValue = this.value;
     }
-    return (10 - overrideValue).toString();
+    return (DEFAULT_PARTY_MAX_COST - overrideValue).toString();
   }
 
   applyStarterChoice(pokemon: PokemonSpecies, valid: Utils.BooleanHolder): boolean {
-    if (speciesStarters[pokemon.speciesId] > 10 - this.value) {
+    if (speciesStarters[pokemon.speciesId] > DEFAULT_PARTY_MAX_COST - this.value) {
       valid.value = false;
       return true;
     }
@@ -723,7 +726,7 @@ export class LowerStarterPointsChallenge extends Challenge {
     if (overrideValue === undefined) {
       overrideValue = this.value;
     }
-    return (10 - overrideValue).toString();
+    return (DEFAULT_PARTY_MAX_COST - overrideValue).toString();
   }
 
   applyStarterPoints(points: Utils.NumberHolder): boolean {
diff --git a/src/data/move.ts b/src/data/move.ts
index a2b879a388b..8616c4caf9b 100644
--- a/src/data/move.ts
+++ b/src/data/move.ts
@@ -5825,7 +5825,7 @@ export class ResistLastMoveTypeAttr extends MoveEffectAttr {
   getCondition(): MoveConditionFunc {
     return (user, target, move) => {
       const moveHistory = target.getLastXMoves();
-      return !!moveHistory.length;
+      return moveHistory.length !== 0;
     };
   }
 }
@@ -8691,8 +8691,8 @@ export function initMoves() {
     new AttackMove(Moves.MALIGNANT_CHAIN, Type.POISON, MoveCategory.SPECIAL, 100, 100, 5, 50, 0, 9)
       .attr(StatusEffectAttr, StatusEffect.TOXIC)
   );
-  allMoves.map(m=>{
-    if (m.getAttrs(StatChangeAttr).some(a=> a.selfTarget && a.levels < 0)) {
+  allMoves.map(m => {
+    if (m.getAttrs(StatChangeAttr).some(a => a.selfTarget && a.levels < 0)) {
       selfStatLowerMoves.push(m.id);
     }
   });
diff --git a/src/data/pokemon-forms.ts b/src/data/pokemon-forms.ts
index d6fe12a8186..7391a92005f 100644
--- a/src/data/pokemon-forms.ts
+++ b/src/data/pokemon-forms.ts
@@ -138,7 +138,7 @@ export class SpeciesFormChange {
   public formKey: string;
   public trigger: SpeciesFormChangeTrigger;
   public quiet: boolean;
-  public conditions: SpeciesFormChangeCondition[];
+  public readonly conditions: SpeciesFormChangeCondition[];
 
   constructor(speciesId: Species, preFormKey: string, evoFormKey: string, trigger: SpeciesFormChangeTrigger, quiet: boolean = false, ...conditions: SpeciesFormChangeCondition[]) {
     this.speciesId = speciesId;
@@ -378,7 +378,7 @@ export function getSpeciesFormChangeMessage(pokemon: Pokemon, formChange: Specie
 /**
  * Gives a condition for form changing checking if a species is registered as caught in the player's dex data.
  * Used for fusion forms such as Kyurem and Necrozma.
- * @param species
+ * @param species {@linkcode Species}
  * @returns A {@linkcode SpeciesFormChangeCondition} checking if that species is registered as caught
  */
 function getSpeciesDependentFormChangeCondition(species: Species): SpeciesFormChangeCondition {
diff --git a/src/data/terrain.ts b/src/data/terrain.ts
index 507557eaf9f..d0b2fb53d3e 100644
--- a/src/data/terrain.ts
+++ b/src/data/terrain.ts
@@ -61,7 +61,7 @@ export class Terrain {
         const priority = new Utils.IntegerHolder(move.priority);
         applyAbAttrs(IncrementMovePriorityAbAttr, user, null, move, priority);
         // Cancels move if the move has positive priority and targets a Pokemon grounded on the Psychic Terrain
-        return priority.value > 0 && user.getOpponents().filter(o => targets.includes(o.getBattlerIndex()) && o.isGrounded()).length > 0;
+        return priority.value > 0 && user.getOpponents().some(o => targets.includes(o.getBattlerIndex()) && o.isGrounded());
       }
     }
 
diff --git a/src/data/type.ts b/src/data/type.ts
index cf3bc85ab48..1330eb83f4b 100644
--- a/src/data/type.ts
+++ b/src/data/type.ts
@@ -505,7 +505,7 @@ export function getTypeDamageMultiplier(attackType: integer, defType: integer):
  * Retrieve the types resisting a given type
  * @returns An array populated with Types, or an empty array if no resistances exist (Unknown or Stellar type)
  */
-export function getTypeResistances(type: integer): Type[] {
+export function getTypeResistances(type: number): Type[] {
   switch (type) {
   case Type.NORMAL:
     return [Type.ROCK, Type.STEEL, Type.GHOST];
diff --git a/src/field/arena.ts b/src/field/arena.ts
index 7d1046986a5..efbcdcd6727 100644
--- a/src/field/arena.ts
+++ b/src/field/arena.ts
@@ -638,7 +638,9 @@ export class Arena {
     }
   }
 
-  /** Clears terrain and arena tags when entering new biome or trainer battle. */
+  /**
+   * Clears terrain and arena tags when entering new biome or trainer battle.
+   */
   resetArenaEffects(): void {
     this.trySetTerrain(TerrainType.NONE, false, true);
     this.removeAllTags();
diff --git a/src/field/pokemon.ts b/src/field/pokemon.ts
index f630cc16a48..7f6c8d11e31 100644
--- a/src/field/pokemon.ts
+++ b/src/field/pokemon.ts
@@ -1241,14 +1241,12 @@ export default abstract class Pokemon extends Phaser.GameObjects.Container {
     }
 
     const immuneTags = this.findTags(tag => tag instanceof TypeImmuneTag && tag.immuneType === moveType);
-    immuneTags.forEach(tag => {
-      if (move !== undefined) {
-        const hitsTagAttrs = move.getAttrs(HitsTagAttr).filter(attr => attr.tagType === tag.tagType);
-        if (hitsTagAttrs.length === 0) {
-          multiplier = 0;
-        }
+    for (const tag of immuneTags) {
+      if (move && !move.getAttrs(HitsTagAttr).some(attr => attr.tagType === tag.tagType)) {
+        multiplier = 0;
+        break;
       }
-    });
+    }
 
     return multiplier;
   }
@@ -1949,7 +1947,7 @@ export default abstract class Pokemon extends Phaser.GameObjects.Container {
         }
 
         const targetCount = getMoveTargets(source, move.id).targets.length;
-        const targetMultiplier = targetCount > 1 ? 0.75 : 1;
+        const targetMultiplier = targetCount > 1 ? 0.75 : 1; // 25% damage debuff on multi-target hits (even if it's immune)
 
         applyMoveAttrs(VariableAtkAttr, source, this, move, sourceAtk);
         applyMoveAttrs(VariableDefAttr, source, this, move, targetDef);
@@ -2282,7 +2280,7 @@ export default abstract class Pokemon extends Phaser.GameObjects.Container {
 
   lapseTags(lapseType: BattlerTagLapseType): void {
     const tags = this.summonData.tags;
-    tags.filter(t => lapseType === BattlerTagLapseType.FAINT || ((t.lapseType.some(lType => lType === lapseType)) && !(t.lapse(this, lapseType)))).forEach(t => {
+    tags.filter(t => lapseType === BattlerTagLapseType.FAINT || ((t.lapseTypes.some(lType => lType === lapseType)) && !(t.lapse(this, lapseType)))).forEach(t => {
       t.onRemove(this);
       tags.splice(tags.indexOf(t), 1);
     });
diff --git a/src/modifier/modifier-type.ts b/src/modifier/modifier-type.ts
index fb2264fab8f..78af578c312 100644
--- a/src/modifier/modifier-type.ts
+++ b/src/modifier/modifier-type.ts
@@ -572,7 +572,7 @@ export class PokemonLevelIncrementModifierType extends PokemonModifierType {
     if (hasCandyJar) {
       levels += hasCandyJar.stackCount;
     }
-    return i18next.t("modifierType:ModifierType.PokemonLevelIncrementModifierType.description", {levels });
+    return i18next.t("modifierType:ModifierType.PokemonLevelIncrementModifierType.description", { levels });
   }
 }
 
@@ -1569,7 +1569,7 @@ const modifierPool: ModifierPool = {
         p => !p.getHeldItems().some(i => i instanceof Modifiers.PokemonResetNegativeStatStageModifier && i.stackCount >= i.getMaxHeldItemCount(p)) &&
           (checkedAbilities.some(a => p.hasAbility(a, false, true)) || p.getMoveset(true).some(m => selfStatLowerMoves.includes(m.moveId)))).length;
       // If a party member has one of the above moves or abilities and doesn't have max herbs, the herb will appear more frequently
-      return 3*(weightMultiplier? 2: 1)+(weightMultiplier? weightMultiplier-1: 0);
+      return 3 * (weightMultiplier ? 2: 1) + (weightMultiplier ? weightMultiplier - 1 : 0);
     }, 10),
     new WeightedModifierType(modifierTypes.REVIVER_SEED, 4),
     new WeightedModifierType(modifierTypes.CANDY_JAR, 5),
diff --git a/src/phases.ts b/src/phases.ts
index 15fd1975d1c..ceefc34ba17 100644
--- a/src/phases.ts
+++ b/src/phases.ts
@@ -1588,8 +1588,6 @@ export class SwitchSummonPhase extends SummonPhase {
       }
     }
 
-    // if doReturn === False OR slotIndex !== -1 (slotIndex is valid) and the pokemon doesn't exist/is false
-    // then switchAndSummon(), manually pick pokemon to switch into
     if (!this.doReturn || (this.slotIndex !== -1 && !(this.player ? this.scene.getParty() : this.scene.getEnemyParty())[this.slotIndex])) {
       if (this.player) {
         return this.switchAndSummon();
@@ -3321,7 +3319,7 @@ export class StatChangePhase extends PokemonPhase {
 
       applyPostStatChangeAbAttrs(PostStatChangeAbAttr, pokemon, filteredStats, this.levels, this.selfTarget);
 
-      //Look for any other stat change phases; if this is the last one, do White Herb check
+      // Look for any other stat change phases; if this is the last one, do White Herb check
       const existingPhase = this.scene.findPhase(p => p instanceof StatChangePhase && p.battlerIndex === this.battlerIndex);
       if (!(existingPhase instanceof StatChangePhase)) {
         // Apply White Herb if needed