int led1 = D3;
int led2 = D2;

//Program the LED’s to alternate blinks i.e. when LED 1 turns on, LED 2 turns off, then when LED 2 turns on, LED 1 turns off.


void setup() {
   pinMode(led1, OUTPUT);
   pinMode(led2, OUTPUT);
   
}
void loop() {
    
    digitalWrite(led1, HIGH);
    delay(500);
    digitalWrite(led1, LOW);
    
    digitalWrite(led2, HIGH);
    delay(500);
    digitalWrite(led2, LOW);

}