Game Project: Space Hero - Beginning HTML5 Games with CreateJS - page 243

The class starts with some constants for an explosion event, the offset for the explosion sequence, and the time
the ship should be invincible after a new life starts. They are followed by some Boolean variables that determine if the
ship is invincible or if it should die in the next render cycle. Some speed and position values are also declared.
The takeDamage method is called when a bullet collides with it. This will play the sequence "heroHit" , which
will cause a white, glowing shimmer. The explode method will be called from the game in the render cycle, which
will play the explosion frames and an explosion sound. The registration points are adjusted so that the explosion will
be properly placed. A listener is set on this animation, which will fire explosionComplete to stop the animation and
dispatch the EXPLOSION_COMPLETE event.
The reset method resets shouldDie to false , puts the frame back on idle, and resets its registration points. Lastly,
the makeInvincible method prevents damage from being inflicted on the ship by setting isInvincible to true and
setting its alpha value to .4. The invincibility is reset with a setTimeout method using the INVINCIBLE_TIME constant.
Creating the Enemy Ships
There are two enemies in the game, each with their own damage animation frames. These ships will periodically
move down the screen and fire bullets that the hero must dodge. The frames that make up the enemy ships are
demonstrated in Figure 11-4 .
Figure 11-4. The sprite frames for the enemy ships
Although there are two enemy ships, only one sprite class will be created. This class will randomly decide what
the ship's type should be, 1 or 2, and display the appropriate frame. The type property will also dictate the amount
of hit points it should have and the total points it will give when destroyed. The complete EnemyShip class is shown
in Listing 11-5.
Listing 11-5. The EnemyShip Class, Declared in EnemyShip.js
(function (window) {
window.game = window.game || {}
function EnemyShip(startX) {
this.initialize(startX);
}
var p = EnemyShip.prototype = new createjs.Sprite();
p.Sprite_initialize = p.initialize;
p.type = null;
p.HP = null;
p.points = null;