Explosion.cs

using System;
using System.Drawing;

namespace Asteroids
{
	/// <summary>
	/// Summary description for Explosion.
	/// </summary>
	class Explosion : ScreenObject
	{
      const int NUM_EXP_POINTS = 22; // more points is more dazzling
      const int EXPLOSION_LIFE = (int)FPS/2; // default life of explosion is 1/2 sec
      int lifeLeft;
      Point[] ptPoints;
      Point[] ptPointsVelocity;
      
		public Explosion(Point ptExplosion, double timeFactor) : base(ptExplosion)
		{
         lifeLeft = (int)(EXPLOSION_LIFE*timeFactor);
         ptPoints = new Point[NUM_EXP_POINTS];
         ptPointsVelocity = new Point[NUM_EXP_POINTS];
         for (int i = 0; i<NUM_EXP_POINTS; i++)
         {
            ptPoints[i] = ptExplosion;
            ptPointsVelocity[i] = new Point((int)((rndGen.Next(1200)-600)/FPS), 
                                            (int)((rndGen.Next(1200)-600)/FPS));
         }
		}

      public override void InitPoints()
      {
         // Explosions are self-drawn
         // so do not initialize points in the base class
      }

      public override bool Move()
      {
         if (lifeLeft > 0)
         {
            for (int i = 0; i<NUM_EXP_POINTS; i++)
            {
               ptPoints[i].X += ptPointsVelocity[i].X;
               ptPoints[i].Y += ptPointsVelocity[i].Y;            

               if (ptPoints[i].X < 0)
                  ptPoints[i].X = iMaxX-1;
               if (ptPoints[i].X >= iMaxX)
                  ptPoints[i].X = 0;
               if (ptPoints[i].Y < 0)
                  ptPoints[i].Y = iMaxY-1;
               if (ptPoints[i].Y >= iMaxY)
                  ptPoints[i].Y = 0;
            }
            lifeLeft -= 1;
            return true;
         }
         else
            return false;
      }

      public override void Draw(ScreenCanvas sc, int iPictX, int iPictY)
      {         
         for (int i = 0; i<NUM_EXP_POINTS; i++)
         {
            Point ptDraw = new Point((int)(ptPoints[i].X / (double)iMaxX * iPictX),
                                     (int)(ptPoints[i].Y / (double)iMaxY * iPictY));

            Point ptDraw2 = new Point(ptDraw.X + 1, ptDraw.Y+1);            

            sc.AddLine(ptDraw, ptDraw2, GetRandomFireColor());
         }
      }
	}
}