// GLOBALS & CONSTANTS
int LED_PIN = 7;
int BTN_PIN = 8;

void setup() {
  pinMode(LED_PIN, OUTPUT);

  // INPUT_PULLUP necessary for the button, since there’s no external resistor
  pinMode(BTN_PIN, INPUT_PULLUP);
}

void loop() {
  int btn_val = digitalRead(BTN_PIN);
  // Since BTN_PIN uses INPUT_PULLUP, if it's not pressed, the value will be 1, meaning it's reverse.
  // (Remember the second example from the first lab, where the values became 0 only if you pressed the button)

  // Perform a XOR operation to "toggle" the value
  int led_val = btn_val ^ 1;

  // Write the value to the LED
  digitalWrite(LED_PIN, led_val);
}