#define BUTTON_PIN 4
#define DOWN LOW


void setup() {
  // initialize digital pin LED_BUILTIN as an output.
  pinMode(BUTTON_PIN, INPUT);
  pinMode(LED_BUILTIN, OUTPUT);
}

// void loop() {
//   if (digitalRead(BUTTON_PIN) == DOWN) {
//     digitalWrite(LED_BUILTIN, HIGH);  // turn the LED on (HIGH is the voltage level)
//   } else {
//     digitalWrite(LED_BUILTIN, LOW);  // turn the LED on (HIGH is the voltage level)
//   }
// }

// void loop() {
//   int val;
//   val = digitalRead(BUTTON_PIN);
//     digitalWrite(LED_BUILTIN, !val);  // turn the LED on (HIGH is the voltage level)
// }  

void loop() {

  digitalWrite(LED_BUILTIN, !digitalRead(BUTTON_PIN));  // turn the LED on (HIGH is the voltage level)
}