Journey of Windows 8 Game (SkyWar) for Intel App Up Using MonoGame Framework

using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Content;
using Microsoft.Xna.Framework.Graphics;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace SkyWar
{
    class AliensComponent
    {
        GameplayScreen _gameScreen;
        GameData _gameData;
        BossAlien bossAlien = null;

        Alien[] _aliens = new Alien[40];        
        int _currentAlienIndex;
        Random _rnd = new Random();
        TimeSpan _elapsedTime;
        int _currentLiveAliens, _totalKilledAliens;
        private TimeSpan _delayCount, _delay;
        public TimeSpan Delay
        {
            get { return _delay; }
            set
            {
                _delay = value;
                _delayCount = TimeSpan.Zero;
            }
        }
        internal IEnumerable<Alien> Aliens { get { return _aliens; } }
        public BossAlien BossAlien { get { return bossAlien; } }
        // alien bullets
        Sprite[] _bullets = new Sprite[40];
        //SoundEffectInstance[] _bulletSoundInst = new SoundEffectInstance[24];
        //SoundEffect _bulletSound;
        Texture2D _texture;
        int _totalBullets, _currentBullet;

        public AliensComponent(GameplayScreen gpScreen, ContentManager content)
        {
            _gameScreen = gpScreen;
            _gameData = GameData.GetGameDataInstance();
            _texture = content.Load<Texture2D>("images/laser1");
        }

        public void Update(GameTime gameTime)
        {
            // get current level data
            LevelData data = _gameScreen.GetCurrentLevelData();

            if (data == null)
            {
                _gameData.IsGameCompleted = true;
                return;
            }
            foreach (var bullet in _bullets)
            {
                if (bullet != null && bullet.Active)
                {
                    bullet.Update(gameTime);
                    if (bullet.Position.Y > _gameData.GameScreenHeight + 30)
                    {
                        bullet.Active = false;
                        _totalBullets--;
                    }
                    else if (bullet.Collide(_gameScreen.SpaceShipComponent.BoundingBox))
                    {
                        _gameScreen.SpaceShipComponent.PlayerHit();
                        bullet.Active = false;
                        _totalBullets--;
                    }
                }
            }

            if (Delay > TimeSpan.Zero)
            {
                if ((_delayCount += gameTime.ElapsedGameTime) >= Delay)
                    Delay = TimeSpan.Zero;
            }
            
            if (_delay == TimeSpan.Zero && (_elapsedTime += gameTime.ElapsedGameTime) > data.AlienGenerationTime)
            {
                _elapsedTime = TimeSpan.Zero;
                var alien = CreateAlien(data);
                if (alien != null)
                {
                    _currentLiveAliens++;
                    while (_aliens[_currentAlienIndex] != null && _aliens[_currentAlienIndex].Active)
                        _currentAlienIndex = (_currentAlienIndex + 1) % _aliens.Length;
                    _aliens[_currentAlienIndex] = alien;
                }
            }

            foreach (var alien in _aliens)
                if (alien != null && alien.Active)
                {
                    alien.Update(gameTime);
                    if (!alien.IsDead && _gameScreen.SpaceShipComponent.IsSpaceShipActive && alien.Collide(_gameScreen.SpaceShipComponent.BoundingBox))
                    {
                        alien.Hit();
                        _gameScreen.SpaceShipComponent.PlayerHit();
                        if (_totalKilledAliens < data.TotalAliensToFinish)
                            _totalKilledAliens = 0;
                    }
                    if (_delay == TimeSpan.Zero && _totalBullets < data.MaxAlienBullets && _rnd.Next(100) < data.FireChance)
                        CreateBullet(alien);
                }

            if (bossAlien != null && bossAlien.Active && (!bossAlien.IsDead))
            {
                bossAlien.Update(gameTime);
                if (!bossAlien.IsDead && _gameScreen.SpaceShipComponent.IsSpaceShipActive && bossAlien.Collide(_gameScreen.SpaceShipComponent.BoundingBox))
                {
                    bossAlien.Hit();
                    _gameScreen.SpaceShipComponent.PlayerHit();
                }
                if (_delay == TimeSpan.Zero && _totalBullets < data.MaxAlienBullets && _rnd.Next(100) < data.FireChance)
                    CreateBullet(bossAlien);
            }
        }

        private Alien CreateAlien(LevelData data)
        {
            if (_currentLiveAliens > data.MaxActiveAliens) return null;

            if (_totalKilledAliens == data.TotalAliensToFinish)
            {
                _totalKilledAliens++;
                bossAlien = CreateBoss(data);
                bossAlien.Killed += delegate
                {
                    _currentLiveAliens--;
                    _gameScreen.InitLevel(_gameScreen.Level + 1);
                    _totalKilledAliens = 0;
                };
                return null;
            }

            int chance = 0;
            int value = _rnd.Next(100);
            foreach (var sd in data.SelectionData)
            {
                if (value < sd.Chance + chance)
                {
                    Alien alien = new Alien(sd.Alien, false);
                    alien.Position = new Vector2((float)(_rnd.NextDouble() * _gameData.GameScreenWidth), -50);
                    alien.Velocity = new Vector2((float)(_rnd.NextDouble() * alien.Type.MaxXSpeed * 2 - alien.Type.MaxXSpeed), (float)(_rnd.NextDouble() * alien.Type.MaxYSpeed + 2));
                    alien.Scale = 0.7f;
                    _aliens[_currentAlienIndex] = alien;
                    alien.OutOfBounds += a =>
                    {
                        _currentLiveAliens--;
                    };
                    alien.Killed += a =>
                    {
                        _currentLiveAliens--;
                        _totalKilledAliens++;
                    };
                    return alien;
                }
                chance += sd.Chance;
            }
            return null;
        }
        private BossAlien CreateBoss(LevelData data)
        {
            BossAlien alien = new BossAlien(data.Boss);
            alien.Position = new Vector2((float)(_rnd.NextDouble() * _gameData.GameScreenWidth), 10);
            alien.Velocity = new Vector2((float)(_rnd.NextDouble() * alien.Type.MaxXSpeed * 4 - alien.Type.MaxXSpeed), 0.0f);
            alien.Scale = 2.3f;
            return alien;
        }

        private void CreateBullet(Sprite alien)
        {
            while (_bullets[_currentBullet] != null && _bullets[_currentBullet].Active)
                _currentBullet = (_currentBullet + 1) % _bullets.Length;
            Sprite bullet = _bullets[_currentBullet];
            if (bullet == null)
            {
                bullet = new Sprite(_texture, new Rectangle(0, 0, 16, 46));
                bullet.Scale = 0.5f;
                bullet.ZLayer = .5f;
                //bullet.Color = Color.White;
                _bullets[_currentBullet] = bullet;
                //_bulletSoundInst[_currentBullet] = _bulletSound.CreateInstance();
                //_bulletSoundInst[_currentBullet].Volume = .7f;
            }
            bullet.Position = alien.Position + new Vector2(-2, alien.ActualHeight / 2);
            bullet.Velocity.Y = alien.Velocity.Y > 0 ? 1.8f * alien.Velocity.Y : _rnd.Next(10) + 3;
            bullet.Active = true;
            //_bulletSoundInst[_currentBullet].Play();
            _totalBullets++;
        }

        public void Draw(GameTime gameTime, SpriteBatch spbatch)
        {
            foreach (var alien in _aliens)
                if (alien != null && alien.Active)
                    alien.Draw(gameTime, spbatch);

            foreach (var bullet in _bullets)
                if (bullet != null)
                    bullet.Draw(gameTime, spbatch);

            if (bossAlien != null && bossAlien.Active && (!bossAlien.IsDead))
                bossAlien.Draw(gameTime, spbatch);
        }
    }
}