#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

#define SCREEN_WIDTH 128 // OLED width,  in pixels
#define SCREEN_HEIGHT 64 // OLED height, in pixels
#define BUTTON_PIN 4

bool btnON = true;

Adafruit_SSD1306 oled(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);

void setup() {
  Serial.begin(9600);
  pinMode(BUTTON_PIN, INPUT_PULLUP);
  if (!oled.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println(F("failed to start SSD1306 OLED"));
    while (1);
  }

  delay(1000);
  oled.clearDisplay();
  oled.setTextSize(3);
  oled.setTextColor(WHITE);

}

int lastState = HIGH;

void loop() {

  int value = digitalRead((BUTTON_PIN));

  if (lastState != value) {
    lastState = value;
    if (value == HIGH) {
      if(btnON) {
        btnON = false;
      } else {
        btnON = true;
      }
    }
  }

  if(btnON) {
      oled.clearDisplay();
      oled.setCursor(0, 2);
      oled.println("ON");
      oled.display();
  } else {
      oled.clearDisplay();
      oled.setCursor(0, 2);
      oled.println("OFF");
      oled.display();
  }

}