#define BUTTON_PIN 2
#define DOWN LOW
#define UP HIGH



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

//  some people build their if statements like this
// 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)
//   }

// }