#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27, 20, 4);
void setup()
{
// put your setup code here, to run once:
Serial.begin(9600);
lcd.init();
lcd.backlight();
}
int x = 0;
int y = 0;
void loop() 
{
for (y=0; y<=3;)
{
  for (x=0; x <=19; x++)
  {
    lcd.setCursor(x, y);
    lcd.print("O");
    delay(100);
    lcd.clear();
  }
  y++;
}
for ( y=3; y>=0; y--)
{
  for ( x=19; x >=0; x--)
  {
    lcd.setCursor(x, y);
    lcd.print("O");
    delay(100);
    lcd.clear();
  }
}
}