// Taken from "Arduino INPUT_PULLUP Explained (pinMode)"
// https://roboticsbackend.com/arduino-input_pullup-pinmode/

#define BUTTON_PIN 4

void setup() {
  Serial.begin(9600);
  pinMode(BUTTON_PIN, INPUT);
}

void loop() {
  Serial.println(digitalRead(BUTTON_PIN));
  delay(100);
}