const int LED_PIN1 = 2;
const int LED_PIN2 = 4;
const int LED_PIN3 = 7;
const int LED_PIN4 = 8;

void setup() {
  // put your setup code here, to run once:
  pinMode(LED_PIN1, OUTPUT);
  pinMode(LED_PIN2, OUTPUT);
  pinMode(LED_PIN3, OUTPUT);
  pinMode(LED_PIN4, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
  digitalWrite(LED_PIN1, HIGH);
  delay(1000); // this speeds up the simulation
  digitalWrite(LED_PIN1, LOW);
  delay(1000); // this speeds up the simulation
    digitalWrite(LED_PIN2, HIGH);
  delay(1000); // this speeds up the simulation
  digitalWrite(LED_PIN2, LOW);
  delay(1000); // this speeds up the simulation
    digitalWrite(LED_PIN3, HIGH);
  delay(1000); // this speeds up the simulation
  digitalWrite(LED_PIN3, LOW);
  delay(1000); // this speeds up the simulation
    digitalWrite(LED_PIN4, HIGH);
  delay(1000); // this speeds up the simulation
  digitalWrite(LED_PIN4, LOW);
  delay(1000); // this speeds up the simulation

}