void drawball(int px, int py, bool on){
    for(int x = 0; x < 2; x++){
        for(int y = 0; y < 2; y++){
            oled_write_pixel(px + x, py + y, on);
        }
    }
}

void oled_task_user(void) {
    static int frame = 0;
    static int px = 0, py = 0, pxm = 1, pym = 1;

    frame++;
    if(frame >= 100){
        frame = 0;

        drawball(px, py, false);

        px += pxm;
        if(px <= 0) {
            pxm = 1;
        }else if(px >= OLED_DISPLAY_WIDTH - 2){
            pxm = -1;
        }

        py += pym;
        if(py <= 0) {
            pym = 1;
        }else if(py >= OLED_DISPLAY_HEIGHT - 2){
            pym = -1;
        }

        drawball(px, py, true);
    }
}