Except after my first loop the ball goes off screen. here's my code:
int x=0;
int dir;
boolean flag=true;

void setup() {
  background(0);
  size(400, 400);
  frameRate(10);
}

void draw() {
  background(0);
  fill(64, 63, 160);
  ellipse(200, 50+pow(x, 2), 60, 60);

  fill(22, 99, 8);
  rect(-1, 345, 401, 55);//

  x=x+dir;
  if (50+pow(x, 2)<315 && flag) {
    dir=1;
    flag=false ;
  }
  if (50+pow(x, 2)>315) {
    dir=-1;
  }
  if (50+pow(x, 2)<3)
    flag=true;
  if (50+pow(x, 2)>3)
    flag=false;
}


Any suggestions