int num = 3000;
int i;
int b=255;
boolean go=true;
boolean released=true;
Speck[] speck = new Speck[num];

void setup(){
  size(500,500,P3D);
  background(0);
  for(i=0; i<num*(2/3); i++){
    speck[i]=new Speck(random(width), random(height), random(0,0.2));
  }
  for(i=i; i<num; i++){
    speck[i]=new Speck(random(width), random(height), random(0,0.1));
  }
}

void draw(){
  fill(0,b);
  noStroke();
  rect(0,0,width,height);
  
  if(mousePressed){
    if(mouseX<width&&mouseX>0&&mouseY<height&&mouseY>0){
      for(i=0; i<num; i++){
        speck[i].go(mouseX, mouseY);
      }
    }
  }
  
  if(keyPressed && released){
    switch(key){
      case ' ':
        for(i=0; i<num; i++){
          speck[i].go(random(width), random(height));
        }
        break;
      case 'b':
        if(b==255){
          b=10;
        }else{
          b=255;
        }
        break;
      case 'p':
        go = !go;
      default:
        break;
    }
    released = false;
  }
  
  if(go){
    for(i=0; i<num; i++){
      speck[i].update();
    }
  }
  
  for(i=0; i<num; i++){
    speck[i].display();
  }
}

void keyReleased(){
  released = true;
}

class Speck {
  float x,y;
  float nx, ny;
  float q;
  float temp;
  color c;

  Speck(float x, float y, float q){
    this.x=this.nx=x;
    this.y=this.ny=y;
    this.q=q;
  }

  void go(float nnx, float nny){
    nx=nnx;
    ny=nny;
  }

  void update(){
      if(nx!=x||ny!=y){
        x=((nx-x)*q)+x;
        y=((ny-y)*q)+y;
      }
    temp = (dist(x,y,nx,ny)/(width*.5))*255;
    c = color(255,255-temp,0);
  }

  void display(){
    stroke(c);    
    point(x,y);
  }
}