8. LED Blink

How do you plan to solve it?

const int LEDpin = 11;

void setup() {
  // put your setup code here, to run once:
  pinMode(LEDpin, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
  digitalWrite(LEDpin, LOW);
  delay(400);
  digitalWrite(LEDpin, HIGH);
  delay(800);
}