const byte interruptPin = 2;
volatile byte state = LOW;

void setup() {
  pinMode(12, OUTPUT);
  pinMode(4, OUTPUT);  
  pinMode(5, OUTPUT); 
  pinMode(interruptPin, INPUT_PULLUP);
  attachInterrupt(digitalPinToInterrupt(interruptPin), blink, FALLING);//CHANGE);
  //attachInterrupt(digitalPinToInterrupt(interruptPin), blink2, RISING);
}

void loop() {
  digitalWrite(12, state);
  delay(1000);
  digitalWrite(4,!digitalRead(4));
}

void blink() {
  state = !state;
}

void blink2() {
  digitalWrite(5,!digitalRead(5));
}