#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 = 3;
volatile int count = 0;

const byte symbols[] = {
  B00000001, // smiley face
  B00000010, // heart
};

void setup() {
  display.begin(SSD1306_SWITCHCAPVCC, 0x3C);
  display.display();
  pinMode(buttonPin, INPUT_PULLUP);
  attachInterrupt(digitalPinToInterrupt(buttonPin), buttonPressed, FALLING); //pull up
}

void loop() {
  // put your main code here, to run repeatedly:  
  display.clearDisplay();
  display.setCursor(0, 0);
  display.print("Symbol: ");
  int symbolIndex = count % sizeof(symbols);
  display.write(symbols[symbolIndex]);
  display.display();
  delay(1000);
}

void buttonPressed() {
  count++;
}