// set pin numbers:
const int buttonPin = 3;     // the number of the pushbutton pin
const int ledPin =  7;       // the number of the LED pin
// variables will change:
int buttonState = 0;         // variable for reading the pushbutton status
bool led_on;
void setup() {
  // initialize the LED pin as an output:
  pinMode(ledPin, OUTPUT);
  // initialize the pushbutton pin as an input:
  pinMode(buttonPin, INPUT);
  led_on = true;
}
void loop() {
  // read the state of the pushbutton value:
  buttonState = digitalRead(buttonPin);
  // check if the pushbutton is pressed.
  // if it is, the buttonState is HIGH:
  if (buttonState == LOW) {
    // turn LED on:
    digitalWrite(ledPin, HIGH);
  }
  else {
    // turn LED on and off:
    if (led_on) {
      digitalWrite(ledPin, LOW);
      led_on = false;
      delay(200);
    } else {
      digitalWrite(ledPin, HIGH);
      led_on = true;
      delay(200);
    }
  }
}