// this is a comment

// blue led is connected to pin 13
const int blue_led = 9;
//yellow led connected to pin 2
const int red_led = 2;

// this part of code runs once
void setup()
{
  pinMode(blue_led, OUTPUT);
  pinMode(red_led, OUTPUT); // LED is an output
}

void loop()
{
  digitalWrite(blue_led, HIGH); // turns LED on
  digitalWrite(red_led, LOW);
  delay(50); // wait for 1000ms = 1s
  
  digitalWrite(blue_led, LOW); // turns LED off
  digitalWrite(red_led, HIGH);
  delay(50); // wait for 1000ms = 1s
}