Firing the bubble
To fire the bubble, the player must press UP arrow key.
The idea: Detect when the player presses UP arrow key, and then calculate the horizontal and vertical speed of the bubble according to the cannon's rotation.
The development: This part has some similarities with the enemy ships' movement you dealt with during the making of Astro-PANIC!
Before we start checking for the UP arrow key, we'll define the bubble speed and some other variables. Let's make a couple of new declarations:
private const ROT_SPEED:uint=2; private const R:uint=18; private const D:Number=R*Math.sqrt(3); private const DEG_TO_RAD:Number=0.0174532925; private const BUBBLE_SPEED:uint=10; private var cannon:cannon_mc; private var left:Boolean=false; private var ...