!7

p { pMain(HeartBeat); }

public sclass HeartBeat extends PApplet {
  public void settings() { size(600, 200); }
  
  int x = 0;
  float py = 0;
 
  public void setup() {
    background(0);
  }
 
  public void draw() {
    noStroke();
    fill(0,0,0,15);
    rect(0,0,width,height);
    translate(0,height/2);
    x++;
    x%=width;
    float fx = py + random(-20,20);
    stroke(100,255,100);
    noFill();
    line(x-1,py, x,fx);
    py = fx;
    if(py>height/2) py=height/2;
    if(py<-height/2) py=-height/2;
  }
}

Began life as a copy of #1013741