AtomicGameEngine-Examples/AtomicBlaster/CSharp/Resources/Scripts/BlackHole.cs

//---------------------------------------------------------------------------------
// Ported to the Atomic Game Engine
// Originally written for XNA by Michael Hoffman
// Find the full tutorial at: http://gamedev.tutsplus.com/series/vector-shooter-xna/
//----------------------------------------------------------------------------------

using System;
using AtomicEngine;

namespace AtomicBlaster
{
    class BlackHole : Entity
    {
        private static Random rand = new Random();

        private int hitpoints = 10;
        private float sprayAngle = 0;

        public BlackHole(Vector2 position)
        {
            image = Art.BlackHole;
            Position = position;
            Radius = image.Width / 2f;
        }

        public override void Update()
        {
            var entities = EntityManager.GetNearbyEntities(Position, 250);

            foreach (var entity in entities)
            {
                if (entity is Enemy && !(entity as Enemy).IsActive)
                    continue;

                // bullets are repelled by black holes and everything else is attracted
                if (entity is Bullet)
                    entity.Velocity += (entity.Position - Position).ScaleTo(0.3f);
                else
                {
                    var dPos = Position - entity.Position;
                    var length = dPos.Length;

                    entity.Velocity += dPos.ScaleTo(MathHelper.Lerp(2, 0, length / 250f));
                }
            }

            // The black holes spray some orbiting particles. The spray toggles on and off every quarter second.
            if ((GameRoot.ElapsedTime * 1000 / 250) % 2 == 0)
            {
                Vector2 sprayVel = MathUtil.FromPolar(sprayAngle, rand.NextFloat(12, 15));
                Color color = ColorUtil.HSVToColor(5, 0.5f, 0.8f);  // light purple
                Vector2 pos = Position + 2f * new Vector2(sprayVel.Y, -sprayVel.X) + rand.NextVector2(4, 8);
                var state = new ParticleState()
                {
                    Velocity = sprayVel,
                    LengthMultiplier = 1,
                    Type = ParticleType.Enemy
                };

                GameRoot.ParticleManager.CreateParticle(Art.LineParticle, pos, color, 190, 1.5f, state);
            }

            // rotate the spray direction
            sprayAngle -= MathHelper.TwoPi / 50f;

            GameRoot.Grid.ApplyImplosiveForce((float)Math.Sin(sprayAngle / 2) * 10 + 20, Position, 200);
        }

        public void WasShot()
        {
            hitpoints--;
            if (hitpoints <= 0)
            {
                IsExpired = true;
                PlayerStatus.AddPoints(5);
                PlayerStatus.IncreaseMultiplier();
            }


            float hue = (float)((3 * GameRoot.ElapsedTime) % 6);
            Color color = ColorUtil.HSVToColor(hue, 0.25f, 1);
            const int numParticles = 150;
            float startOffset = rand.NextFloat(0, MathHelper.TwoPi / numParticles);

            for (int i = 0; i < numParticles; i++)
            {
                Vector2 sprayVel = MathUtil.FromPolar(MathHelper.TwoPi * i / numParticles + startOffset, rand.NextFloat(8, 16));
                Vector2 pos = Position + 2f * sprayVel;
                var state = new ParticleState()
                {
                    Velocity = sprayVel,
                    LengthMultiplier = 1,
                    Type = ParticleType.IgnoreGravity
                };

                GameRoot.ParticleManager.CreateParticle(Art.LineParticle, pos, color, 90, 1.5f, state);
            }

            //Sound.Explosion.Play(0.5f, rand.NextFloat(-0.2f, 0.2f), 0);
        }

        public void Kill()
        {
            hitpoints = 0;
            WasShot();
        }

        public override void Draw(/*SpriteBatch spriteBatch*/)
        {
            // make the size of the black hole pulsate
            float scale = 1 + 0.1f * (float)Math.Sin(10 * GameRoot.ElapsedTime);
            CustomRenderer.Draw(image, Position, color, Orientation, Size / 2f, scale, 0);
        }
    }
}