int i = 99;
void setup() {
  size(200, 140);
}
void draw() {
  background(0);
  text(i + " bottles of beer on the wall\n"
    + i + " bottles of beer\nTake one down, pass it around\n"
    + (i - 1) + " bottles of beer on the wall\n\n",
    10, 20);
  if (frameCount%240==239) next();  // auto-advance every 4 secs
}
void mouseReleased() {
  next();  // manual advance
}
void next() {
  i = max(i-1, 1);  // stop decreasing at 1-0 bottles
}
