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

#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
#define SCREEN_MIDDLE SCREEN_HEIGHT / 2
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);

int i, buttonPin = 2;
bool oldButtonState;

void setup() {
  pinMode(buttonPin, INPUT_PULLUP);
  if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println(F("SSD1306 failed"));
    while (1);
  }
  display.clearDisplay();
}

void loop() {
  display.drawLine(i, 0, i, 63, BLACK); // verticle line to erase trace
  display.display();
  if (digitalRead(buttonPin)) {
    display.drawPixel(i, SCREEN_MIDDLE - 10, WHITE);
  } else {
    display.drawPixel(i, SCREEN_MIDDLE + 10, WHITE);
  }
  display.display();
  i++; // next pixel
  if (i == 128) { // OLED right edge
    i = 0; // reset i
  }
}