feat(#10): reset camera position after changing level

modules/event-emitter.js

@@ -0,0 +1,32 @@
+class EventEmitterSingleton {
+  static instance;
+  eventEmitter;
+
+  constructor() {
+    this.eventEmitter = {};
+  }
+
+  static getInstance() {
+    if (!EventEmitterSingleton.instance) {
+      EventEmitterSingleton.instance = new EventEmitterSingleton();
+    }
+    return EventEmitterSingleton.instance;
+  }
+
+  on(eventName, callback) {
+    if (!this.eventEmitter[eventName]) {
+      this.eventEmitter[eventName] = [];
+    }
+    this.eventEmitter[eventName].push(callback);
+  }
+
+  emit(eventName, ...args) {
+    if (this.eventEmitter[eventName]) {
+      this.eventEmitter[eventName].forEach((callback) => {
+        callback(...args);
+      });
+    }
+  }
+}
+
+export const eventEmitter = EventEmitterSingleton.getInstance();