Processing(.js) sketch of a "cell" pulsing.

cell.js

// comments go here
boolean expanding = true;
int change = 0;

void setup()
{
  size(200,200);
  background(125);
  fill(255);
  frameRate(10);
}

void draw(){
  background( 100 ); 
  stroke(0, 0, 0);
  change += (expanding) ? 1 : -1;
  if(change == 0) {
    expanding = true;
  } else if(change >= 5) {
    expanding = false;
  } 
  
  noFill();
  bezier(110, 50,  150 + (change * 2), 5,  150 + (change * 2), 145,  110, 100);
  
  bezier(110, 50,  105, 55 + (change),  95, 55 + (change),  90, 50);
  bezier(110, 100,  105, 95 - (change),  95, 95 - (change),  90, 100);  
  bezier(90, 50,  50 - (change * 2), 5,  50 - (change * 2), 145,  90, 100);
}