void draw() {
  int d = 80; // This variable can be used everywhere in draw()
  if (d > 50) {
    int x = 10; // This variable can be used only in this if block
    line(x, 40, x+d, 40);
  }
  line(0, 50, d, 50);
  line(x, 60, x+d, 60); // ERROR! x can't be read outside block
}