refactor: centralize system names, component types, entity types, and animation states into a new Constants module.

src/core/Constants.js

@@ -0,0 +1,62 @@
+/**
+ * Centralized Constants and Enums
+ */
+
+export const GameState = {
+  START: 'start',
+  PLAYING: 'playing',
+  PAUSED: 'paused',
+  GAME_OVER: 'gameOver'
+};
+
+export const ComponentType = {
+  POSITION: 'Position',
+  VELOCITY: 'Velocity',
+  SPRITE: 'Sprite',
+  HEALTH: 'Health',
+  COMBAT: 'Combat',
+  AI: 'AI',
+  EVOLUTION: 'Evolution',
+  STATS: 'Stats',
+  SKILLS: 'Skills',
+  SKILL_PROGRESS: 'SkillProgress',
+  ABSORBABLE: 'Absorbable',
+  STEALTH: 'Stealth'
+};
+
+export const EntityType = {
+  SLIME: 'slime',
+  HUMANOID: 'humanoid',
+  BEAST: 'beast',
+  ELEMENTAL: 'elemental',
+  PROJECTILE: 'projectile'
+};
+
+export const AnimationState = {
+  IDLE: 'idle',
+  WALK: 'walk'
+};
+
+export const VFXType = {
+  IMPACT: 'impact',
+  ABSORPTION: 'absorption'
+};
+
+export const SystemName = {
+  MENU: 'MenuSystem',
+  UI: 'UISystem',
+  PLAYER_CONTROLLER: 'PlayerControllerSystem',
+  ABSORPTION: 'AbsorptionSystem',
+  COMBAT: 'CombatSystem',
+  PROJECTILE: 'ProjectileSystem',
+  VFX: 'VFXSystem',
+  MOVEMENT: 'MovementSystem',
+  AI: 'AISystem',
+  DEATH: 'DeathSystem',
+  RENDER: 'RenderSystem',
+  INPUT: 'InputSystem',
+  SKILL_EFFECT: 'SkillEffectSystem',
+  SKILL: 'SkillSystem',
+  STEALTH: 'StealthSystem',
+  HEALTH_REGEN: 'HealthRegenerationSystem'
+};

src/core/Engine.js

@@ -2,6 +2,7 @@ import { System } from './System.js';
 import { Entity } from './Entity.js';
 import { EventBus } from './EventBus.js';
 import { LevelLoader } from './LevelLoader.js';
+import { GameState, SystemName } from './Constants.js';
 
 /**
  * Main game engine - manages ECS, game loop, and systems
@@ -48,8 +49,8 @@ export class Engine {
   }
 
   /**
-         * Emit an event locally
-         */
+   * Emit an event locally
+   */
   emit(event, data) {
     this.events.emit(event, data);
   }
@@ -118,20 +119,21 @@ export class Engine {
     this.deltaTime = Math.min(this.deltaTime, 0.1);
 
     // Update all systems
-    const menuSystem = this.systems.find(s => s.name === 'MenuSystem');
-    const gameState = menuSystem ? menuSystem.getGameState() : 'playing';
-    const isPaused = gameState === 'paused' || gameState === 'start' || gameState === 'gameOver';
+    const menuSystem = this.systems.find(s => s.name === SystemName.MENU);
+    const gameState = menuSystem ? menuSystem.getGameState() : GameState.PLAYING;
+    const isPaused = [GameState.PAUSED, GameState.START, GameState.GAME_OVER].includes(gameState);
+    const unskippedSystems = [SystemName.MENU, SystemName.UI, SystemName.RENDER];
 
     this.systems.forEach(system => {
       // Skip game systems if paused/start menu (but allow MenuSystem, UISystem, and RenderSystem)
-      if (isPaused && system.name !== 'MenuSystem' && system.name !== 'UISystem' && system.name !== 'RenderSystem') {
+      if (isPaused && !unskippedSystems.includes(system.name)) {
         return;
       }
       system.update(this.deltaTime, this.entities);
     });
 
     // Update input system's previous states at end of frame
-    const inputSystem = this.systems.find(s => s.name === 'InputSystem');
+    const inputSystem = this.systems.find(s => s.name === SystemName.INPUT);
     if (inputSystem && inputSystem.updatePreviousStates) {
       inputSystem.updatePreviousStates();
     }

src/core/SpriteLibrary.js

@@ -1,3 +1,5 @@
+import { EntityType, AnimationState } from './Constants.js';
+
 /**
  * Sprite Library defining pixel art grids as 2D arrays.
  * 0: Transparent
@@ -7,8 +9,8 @@
  */
 export const SpriteLibrary = {
   // 8x8 Slime - Bottom-heavy blob
-  slime: {
-    idle: [
+  [EntityType.SLIME]: {
+    [AnimationState.IDLE]: [
       [
         [0, 0, 0, 0, 0, 0, 0, 0],
         [0, 0, 1, 1, 1, 1, 0, 0], // Top
@@ -30,7 +32,7 @@ export const SpriteLibrary = {
         [1, 1, 1, 1, 1, 1, 1, 1]  // Squashed base
       ]
     ],
-    walk: [
+    [AnimationState.WALK]: [
       [
         [0, 0, 1, 1, 1, 1, 0, 0],
         [0, 1, 1, 1, 1, 1, 1, 0],
@@ -55,8 +57,8 @@ export const SpriteLibrary = {
   },
 
   // 8x8 Humanoid - Simple Walk Cycle
-  humanoid: {
-    idle: [
+  [EntityType.HUMANOID]: {
+    [AnimationState.IDLE]: [
       [
         [0, 0, 0, 1, 1, 0, 0, 0],
         [0, 0, 2, 1, 1, 2, 0, 0],
@@ -68,7 +70,7 @@ export const SpriteLibrary = {
         [0, 0, 1, 0, 0, 1, 0, 0]
       ]
     ],
-    walk: [
+    [AnimationState.WALK]: [
       [
         [0, 0, 0, 1, 1, 0, 0, 0],
         [0, 0, 2, 1, 1, 2, 0, 0],
@@ -93,8 +95,8 @@ export const SpriteLibrary = {
   },
 
   // 8x8 Beast - Bounding Cycle
-  beast: {
-    idle: [
+  [EntityType.BEAST]: {
+    [AnimationState.IDLE]: [
       [
         [0, 0, 0, 0, 0, 0, 0, 0],
         [1, 0, 0, 0, 0, 0, 0, 1],
@@ -106,7 +108,7 @@ export const SpriteLibrary = {
         [0, 1, 0, 0, 0, 0, 1, 0]
       ]
     ],
-    walk: [
+    [AnimationState.WALK]: [
       [
         [1, 0, 0, 0, 0, 0, 0, 1],
         [0, 1, 1, 1, 1, 1, 1, 0],
@@ -131,8 +133,8 @@ export const SpriteLibrary = {
   },
 
   // 8x8 Elemental - Floating Pulse
-  elemental: {
-    idle: [
+  [EntityType.ELEMENTAL]: {
+    [AnimationState.IDLE]: [
       [
         [0, 0, 2, 1, 1, 2, 0, 0],
         [0, 1, 1, 2, 2, 1, 1, 0],
@@ -156,8 +158,8 @@ export const SpriteLibrary = {
     ]
   },
 
-  projectile: {
-    idle: [
+  [EntityType.PROJECTILE]: {
+    [AnimationState.IDLE]: [
       [
         [1, 1],
         [1, 1]