int led = 2; //renames pin 2 as led
int delayPeriod = 150;

void setup() {
  pinMode(led, OUTPUT);

}

void loop() {
 int i = 0;
 while (i < 20)
 {
  digitalWrite(led, HIGH);
    delay(delayPeriod);
  digitalWrite(led, LOW);
    delay(delayPeriod);
    i ++; // defines a new value of i by adding 1 to the previous value
 }
delay(3000);
}