// particle.java

public class particle
{  public particle(int c, double d1, double d2, double d3, double d4)
   {  colour = c;   x = d1;   lastx  = d1;
                    y = d2;   lasty  = d2;   xvel = d3;   yvel = d4;
   }
   public int    colour;
   public double x;
   public double y;
   public double lastx;
   public double lasty;
   public double xvel;
   public double yvel;
}