volatile bool isLightOn = false;

void setup() {
  pinMode(2, OUTPUT); //   LED
  pinMode(3, INPUT);  //  interrupt_Pin     int=1

                     //pin_3 <-> [int]1
  attachInterrupt(digitalPinToInterrupt(3), buttonPressed, RISING);
//attachInterrupt(digitalPinToInterrupt(3), buttonPressed, FALLING);
//attachInterrupt(digitalPinToInterrupt(3), buttonPressed, CHANGE);
}

void loop() {}

void buttonPressed() {
  isLightOn = !isLightOn;
  digitalWrite(2, isLightOn ? HIGH : LOW);
}


// wokwi.com/projects/376287050597699585   Switch,nano


// in uno/nano only pin 2 and 3 can use. 2has the priority.