Minimal code for screen on fire effect. Mainly due to XOR, bitwise, modulus operators.

XOR_operator_fire.pde

//based from https://www.dwitter.net/d/21877
float m, t, w=32, X, Y;
void setup() {
  size(1280, 720);
  noStroke();
}
void draw() {
  t+=.1;
  fill(0, 2);
  rect(0, 0, width, height);
  for (int i=768; i>0; i--) {
    fill(m=sin(int(X=i%w)>>round(random(2))^int(t*w+(Y=i/w)))*i, m/4, 0);
    rect(X, Y, 2, 2);
  }
  filter(ERODE);
  copy(this.get(), 2, 0, 30, 16, 0, 0, width, height);
}