"Sometimes in a game you want to be aware of events that occur in your game the whole time, wether it would be to save game statistics or to build an achievement system. For example, your game may need to know when an enemy is killed to save the number of killed enemies, or because there is an achievement when the player kills a given number of enemies.
In this tutorial I will show how to use Phaser.Signal to listen to events in your game in order to save game statistics. We will implement it in a simple space shooter game. At the end, I will briefly explain how to extend this concept to create an achievement system."