In this section, we'll be programming in a Boss AI for the player to fight after a certain time (a minute specifically). Create a missile sprite where its head points downwards (to make launching it from the boss easier to code), and of course, center its origin. Then, create a boss object and a missile object. We'll work on the boss later, but we'll have to reference it in the missile object.

Make the missile object a child of class_enemy, give it a depth of -10, and of course assign it its sprite. In the Create event for the object, give it two variables: hp, which should be set to 5, and dir, which should be set to 270. dir. This will be the default direction of the missile to face.

Now, add a Step event to the object. First call event_inherited(). Next, check if an instance of the boss object collides with the bottom of the missile (using place_meeting). If so, increment y by 5. What this does is have the missile move down out of the boss' launchers until it's outside...