boolean playing = false;
int temps_play, temps_pause, now, pre;

void setup() {
  size (400, 800);
}

void draw() {
  background(255);  fill(0);
  now = millis();
  if (playing) {
    temps_play += now - pre;
  } else {
    temps_pause += now - pre;
  }
  rect(0, height - (float(temps_play) / 100), 200, height);
  rect(200, height - (float(temps_pause) / 100), 400, height);
  pre = now;
}

void keyPressed() {
  if (key == ' ') playing = !playing;
}