int x = 0;
int y = 0;
int center = 200;
float angle = 0;
float r = 0;
int NUM_PARTICLES = 3158;
Particle[] particles = new Particle[ NUM_PARTICLES ];
int recursion = 0;

void setup()
{
  size( 400, 400 );
  background( 0 );
  smooth();
  noStroke();
  ackermann( 2, 56 );
}

void draw()
{
  fill( 0, 20 );
  rect( 0, 0, 400, 400 );

  for ( int i = 0; i < NUM_PARTICLES; i++ )
    particles[ i ].render();
}

int ackermann( int m, int n )
{  
  x = center + (int)( cos( angle ) * r );
  y = center + (int)( sin( angle ) * r );
  angle += .05;
  r += .05;
  int c = max( m, n ) << 3;

  if ( c < 256 )
    particles[ recursion++ ] = new Particle( x, y, c, angle, r );


  /**
   * Ackermann function
   */
  if ( m == 0 ) return n + 1;
  if ( m > 0 && n == 0 )
    return ackermann( m - 1, 1 );
  if ( m > 0 && n > 0 )
    return ackermann( m - 1, ackermann( m, n - 1 ) );
  return 0;
}

class Particle
{

  int _x;
  int _y;
  int _c;
  float _a;
  float _r;
  float _ca;

  Particle( int x, int y, int c, float a, float r )
  {
    _x = x;
    _y = y;
    _c = c;
    _a = a;
    _r = r;
    _ca = 0;
  }

  public void render()
  {
    float clr = cos( _a - _ca ) * 256;
    _c = (int)clr;
    _ca -= .001;

    _x = 200 + (int)( cos( _a ) * _r );
    _y = 200 + (int)( sin( _a ) * _r );
    _a += .02;

    if ( _x < -1 || _x > 401 ||
         _y < -1 || _y > 401 )
      return;
    fill( _c );
    ellipse( _x, _y, 5, 5 );
  }

}