const int butt = 4;
const int led = 2;

bool buttState;
bool buttLastState = HIGH;
bool val;

void setup(){
  pinMode(butt, INPUT_PULLUP);
  pinMode(led, OUTPUT);
}

void loop(){
buttState = digitalRead(butt);
if(buttState == LOW && buttLastState == HIGH)
{
  delay(20);
  buttState = digitalRead(butt);
  if(buttState == LOW && buttLastState == HIGH)
  {
    val = !val;
  }
}
buttLastState = buttState;

 if (val == HIGH){
  digitalWrite(led, HIGH);
 }
 else {
  digitalWrite(led, LOW);
 }
}