#define led1 13
#define led2 12
#define led3 11
#define led4 10
#define interruptPin 3
volatile byte state = LOW;

void setup() {
  pinMode(led1, OUTPUT);
  pinMode(led2, OUTPUT);
  pinMode(led3, OUTPUT);
  pinMode(led4, OUTPUT);
  pinMode(interruptPin, INPUT_PULLUP);
  attachInterrupt(digitalPinToInterrupt(interruptPin),blink,CHANGE);
  Serial.begin(9600);
  
}

void loop() {
  Serial.print("test");
  for(int i=1;i<=20;i++){
    Serial.print("-");
    Serial.print(i);
    delay(250);
    digitalWrite(led1,state);
  }
  Serial.println("");

}
void blink(){
  state = !state;
  Serial.println("");
  Serial.println("Interrupted");
}