A circle drawn using frame loop

increaseingCircle.pde

int diam = 10;

void setup() {
  size(400, 400);
  frameRate(24);
  noStroke();
  fill(255,0,0);
  background(255,255,0);
}
      
void draw() {
  if (diam <= 400) {
    background(180);
    ellipse(width/2, height/2, diam, diam);
    diam += 10;
  }
  
  if (diam > 400) {
    background(180);
    diam = 0;  
  }  
  
}