Blader subclass of Phaser.Sprite for #LOWREZJAM

Blader.js

function Blader(game, x, y, cacheKey) {
    // Call the Phaser.Sprite constructor
    Phaser.Sprite.call(this, game, x, y, cacheKey);
    // Enable physics
    this.game.physics.enable(this);
    // Set the (physics) body to be immovable
    this.immovable = true;
    // Set the initial target coordinates
    this.target = new Phaser.Point(0, 0);
    // Set the 'fly' animation
    this.animations.add('fly', [0, 1], 5, true);
    // Set the velocity to chase another sprite
    this.speed = 90;
    // The 'explosionGroup' for spawning explosions
    this.explosionGroup = new ExplosionGroup(this.game);
    // Set that this sprite is 'alive'
    this.alive = true;
    // Set the distance at which a Blader should
    //  destory() itself.
    this.killDistance = this.width * 24;
}

Blader.prototype = Object.create(Phaser.Sprite.prototype);
Blader.prototype.constructor = Blader;

/*
 * This is called from the main game loop like the following:
 * this.bladerGroup.callAll('updateTarget', null, this.player.x, this.player.y);
 * 
 * It updates the 'target' position for all Bladers in the group
 * 
 */
Blader.prototype.updateTarget = function(x, y) {
    this.target.x = x;
    this.target.y = y;
};

Blader.prototype.update = function() {
    // If the 'target.x' is still 0, don't do anything
    if (this.target.x !== 0) {
        // At some point, the 'target' has been updated, so
        //  we need to move toward the target at the 'speed'
        this.game.physics.arcade.moveToXY(this,
                this.target.x, this.target.y, this.speed);
        // Since we are moving, play the 'fly' animation
        this.play('fly');

        // If the target is greater than 24 * width OR 24 * height away,
        //  go ahead and destory yourself. (If they are that
        //  far away, a Blader cannot ever catch up.)
        if ((this.target.x - this.x) > this.killDistance ||
                (this.target.y - this.y) > this.killDistance) {
            Phaser.Sprite.prototype.destroy.call(this);
        }
    }
};

Blader.prototype.kill = function() {
    // Create an explosion at this position
    this.explosionGroup.explode(this.x, this.y);
    // kill() this sprite by calling Phaser.Sprite's
    //  own kill function and passing 'this'
    Phaser.Sprite.prototype.kill.call(this);
};