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

#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64

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

const int buttonPin = 2;
volatile int buttonState = 0;  //value will change

void setup() {
  pinMode(buttonPin, INPUT);
  attachInterrupt(digitalPinToInterrupt(buttonPin), buttonInterruptHandler, CHANGE);
  display.begin(SSD1306_SWITCHCAPVCC, 0x3C);
  display.display();
}

void loop() {
  if (buttonState) {
    buttonState = 0;
    display.clearDisplay();
    display.setTextSize(3);
    display.setTextColor(WHITE);
    display.setCursor((display.width() - 12) / 2, (display.height() - 16) / 2);
    display.write(234); //ASCII Value (tables online)
    display.display();
    delay(1000);
  }
}

void buttonInterruptHandler() {
  buttonState = 1;
}