Feature: Implement invincibility and combo systems

- Added Invincibility component to manage invincibility state and duration.
- Introduced InvincibilitySystem to handle visual effects during invincibility.
- Updated Game class to integrate combo multiplier mechanics and high score tracking.
- Enhanced UI to display current combo status and high score.
- Configured GameConfig for centralized game settings, including obstacle damage and invincibility duration.
- Updated game logic to reset combo on damage and manage health regeneration.

This update enhances gameplay dynamics by introducing invincibility frames and a scoring combo system.

src/systems/InvincibilitySystem.js

@@ -0,0 +1,49 @@
+import { System } from '../ecs/System.js';
+import { Invincibility } from '../components/Invincibility.js';
+import { MeshComponent } from '../components/MeshComponent.js';
+import { GameConfig } from '../game/GameConfig.js';
+
+/**
+ * InvincibilitySystem - handles invincibility flashing effect
+ */
+export class InvincibilitySystem extends System {
+  constructor() {
+    super();
+    this.flashTimer = 0;
+  }
+
+  /**
+   * Update invincibility timers and flash effect
+   * @param {number} deltaTime - Time since last frame in seconds
+   */
+  update(deltaTime) {
+    const entities = this.getEntities(Invincibility, MeshComponent);
+
+    this.flashTimer += deltaTime;
+
+    for (const entityId of entities) {
+      const invincibility = this.getComponent(entityId, Invincibility);
+      const meshComp = this.getComponent(entityId, MeshComponent);
+
+      if (!invincibility || !meshComp) continue;
+
+      // Update invincibility timer
+      invincibility.update(deltaTime);
+
+      // Flash effect - toggle visibility based on flash rate
+      if (invincibility.getIsInvincible()) {
+        const flashInterval = Math.floor(this.flashTimer / GameConfig.INVINCIBILITY_FLASH_RATE);
+        meshComp.mesh.visible = flashInterval % 2 === 0;
+      } else {
+        // Always visible when not invincible
+        meshComp.mesh.visible = true;
+      }
+    }
+
+    // Reset flash timer periodically to prevent overflow
+    if (this.flashTimer > 10) {
+      this.flashTimer = 0;
+    }
+  }
+}
+