const int buttonPin = 2;
const int ledPin = 11;

int currState = HIGH;
int prevState = HIGH;
int lightState = LOW;

void setup() {
  pinMode(buttonPin, INPUT_PULLUP);
  pinMode(ledPin, OUTPUT);
}

void loop() {
  currState = digitalRead(buttonPin);
  
  if(currState != prevState) {
    
    if(currState == LOW and lightState == LOW) {
      lightState = HIGH;
      digitalWrite(ledPin, lightState);
    }
    else if (currState == LOW and lightState == HIGH) {
      lightState = LOW;
      digitalWrite(ledPin, lightState);
    }
  }
  
  prevState = currState;
  delay(100);   
  
}