#include <Arduino.h>
#include <Wire.h>
#include <U8g2lib.h>
#include <math.h>

// OLED

U8G2_SSD1306_128X64_NONAME_F_HW_I2C u8g2(
  U8G2_R0,
  U8X8_PIN_NONE
);

// Touch / Input Pins

#define PIN_LEFT   D1
#define PIN_RIGHT  D7
#define PIN_DOWN   D8
#define PIN_UP     D0
#define PIN_Q1     D9
#define PIN_Q2     D10

#define N_TOUCH    6
#define THRESHOLD  6

enum TouchIndex {
  T_LEFT = 0,
  T_RIGHT,
  T_DOWN,
  T_UP,
  T_Q1,
  T_Q2
};

const uint8_t touchPins[N_TOUCH] = {
  PIN_LEFT,
  PIN_RIGHT,
  PIN_DOWN,
  PIN_UP,
  PIN_Q1,
  PIN_Q2
};

int touchValue[N_TOUCH];

bool touchedNow[N_TOUCH] = {
  false, false, false,
  false, false, false
};

bool touchedBefore[N_TOUCH] = {
  false, false, false,
  false, false, false
};

// Screen

const int SCREEN_W = 128;
const int SCREEN_H = 64;

const int PLAY_TOP = 11;
const int PLAY_BOTTOM = 61;

// Sprite Sizes

const int PLAYER_W = 14;
const int PLAYER_H = 9;

const int ENEMY_W = 10;
const int ENEMY_H = 7;

const int BOSS_W = 22;
const int BOSS_H = 19;

// Game State

enum GameState {
  STATE_TITLE,
  STATE_PLAYING,
  STATE_BOSS,
  STATE_PAUSED,
  STATE_LEVEL_CLEAR,
  STATE_GAME_OVER
};

GameState gameState = STATE_TITLE;
GameState stateBeforePause = STATE_PLAYING;

// Game Data

unsigned long score = 0;
int lives = 4;

const unsigned long BOSS_SCORE = 800;

// SPACE IMPACT LOGO 128x64

const unsigned char epd_bitmap_co7orh[] PROGMEM = {
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};

// PLAYER SHIP - custom like reference image
// 14x9

const char playerShip[PLAYER_H][PLAYER_W + 1] = {
  "..##..........",
  ".####.........",
  "######........",
  "##.#####......",
  "###########...",
  "##.#####......",
  "######........",
  ".####.........",
  "..##.........."
};

// DEFAULT NORMAL ENEMY 10x7

const unsigned char enemySprite[] PROGMEM = {
  0x20, 0x00,
  0x70, 0x00,
  0xFC, 0x00,
  0xFF, 0x03,
  0xFC, 0x00,
  0x70, 0x00,
  0x20, 0x00
};

// BOSS / KING - custom monster 22x19

const char bossMonster[BOSS_H][BOSS_W + 1] = {
  "........#####..###....",
  ".......##.##.######...",
  "###...#####..#####....",
  "##############.##.....",
  "##.##############.....",
  ".#..###.#.#..#####....",
  ".#####..####..####..##",
  "..##...######....#####",
  ".##...###.###.##.#####",
  ".#....###.###..#######",
  ".#....######....#####.",
  ".#.#.........##.####..",
  ".#######......#####...",
  ".##.#.#.#...##.##.....",
  ".##.####..##.####.....",
  ".#.#.#.....####.##....",
  ".#.......######.##....",
  "..##########.######...",
  ".....###.##...#####..."
};

// Structs

struct Player {
  int x;
  int y;
  bool invincible;
  unsigned long invincibleStart;
};

struct Bullet {
  int x;
  int y;
  bool active;
};

struct EnemyBullet {
  int x;
  int y;
  int vx;
  int vy;
  bool active;
};

struct Enemy {
  int x;
  int y;
  int baseY;
  int hp;
  int speed;
  int movement;
  float phase;
  bool shoots;
  bool active;
  unsigned long lastShot;
};

struct Star {
  int x;
  int y;
  int speed;
};

struct Explosion {
  int x;
  int y;
  int frame;
  bool active;
  unsigned long lastFrame;
};

struct Boss {
  int x;
  int y;
  int hp;
  int maxHP;
  int verticalDirection;
  bool active;
  bool charging;
  bool returning;
  unsigned long lastShot;
  unsigned long lastCharge;
};

// Objects

Player player;

const int MAX_BULLETS = 8;
Bullet bullets[MAX_BULLETS];

const int MAX_ENEMY_BULLETS = 8;
EnemyBullet enemyBullets[MAX_ENEMY_BULLETS];

const int MAX_ENEMIES = 6;
Enemy enemies[MAX_ENEMIES];

const int MAX_STARS = 16;
Star stars[MAX_STARS];

const int MAX_EXPLOSIONS = 6;
Explosion explosions[MAX_EXPLOSIONS];

Boss boss;

// Timers

unsigned long lastPlayerMove = 0;
unsigned long lastBulletUpdate = 0;
unsigned long lastEnemyUpdate = 0;
unsigned long lastEnemySpawn = 0;
unsigned long lastEnemyBulletUpdate = 0;
unsigned long lastStarUpdate = 0;

const unsigned long PLAYER_INTERVAL = 25;
const unsigned long BULLET_INTERVAL = 25;
const unsigned long ENEMY_INTERVAL = 45;
const unsigned long ENEMY_BULLET_INTERVAL = 35;
const unsigned long STAR_INTERVAL = 50;

// Touch Helpers

void updateTouch() {
  const int maxCount = 200;

  for (int i = 0; i < N_TOUCH; i++) {
    touchedBefore[i] = touchedNow[i];

    pinMode(touchPins[i], OUTPUT);
    digitalWrite(touchPins[i], LOW);
    delayMicroseconds(25);

    pinMode(touchPins[i], INPUT_PULLUP);

    int count = 0;

    while (digitalRead(touchPins[i]) == LOW && count < maxCount) {
      count++;
    }

    touchValue[i] = count;
    touchedNow[i] = count > THRESHOLD;
  }
}

bool touchHeld(int index) {
  return touchedNow[index];
}

bool touchPressed(int index) {
  return touchedNow[index] && !touchedBefore[index];
}

// Draw Logo
// bitmap is MSB first

void drawLogo() {
  for (int y = 0; y < 64; y++) {
    for (int x = 0; x < 128; x++) {
      int byteIndex = y * 16 + x / 8;

      uint8_t data = pgm_read_byte(&epd_bitmap_co7orh[byteIndex]);

      if (data & (0x80 >> (x & 7))) {
        u8g2.drawPixel(x, y);
      }
    }
  }
}

// Reset Game

void resetGame() {
  score = 0;
  lives = 4;

  player.x = 12;
  player.y = 32;
  player.invincible = false;
  player.invincibleStart = 0;

  for (int i = 0; i < MAX_BULLETS; i++) {
    bullets[i].active = false;
  }

  for (int i = 0; i < MAX_ENEMY_BULLETS; i++) {
    enemyBullets[i].active = false;
  }

  for (int i = 0; i < MAX_ENEMIES; i++) {
    enemies[i].active = false;
  }

  for (int i = 0; i < MAX_EXPLOSIONS; i++) {
    explosions[i].active = false;
  }

  for (int i = 0; i < MAX_STARS; i++) {
    stars[i].x = random(0, SCREEN_W);
    stars[i].y = random(PLAY_TOP + 2, PLAY_BOTTOM);
    stars[i].speed = random(1, 3);
  }

  boss.active = false;
  boss.hp = 0;

  lastEnemySpawn = millis();

  gameState = STATE_PLAYING;
}

// Player Update

void updatePlayer() {
  if (millis() - lastPlayerMove < PLAYER_INTERVAL) {
    return;
  }

  lastPlayerMove = millis();

  if (touchHeld(T_LEFT)) {
    player.x -= 2;
  }

  if (touchHeld(T_RIGHT)) {
    player.x += 2;
  }

  if (touchHeld(T_UP)) {
    player.y -= 2;
  }

  if (touchHeld(T_DOWN)) {
    player.y += 2;
  }

  player.x = constrain(player.x, 0, SCREEN_W - PLAYER_W - 8);
  player.y = constrain(player.y, PLAY_TOP + 1, PLAY_BOTTOM - PLAYER_H);

  if (player.invincible && millis() - player.invincibleStart > 1200) {
    player.invincible = false;
  }
}

// Player Fire

void fireBullet() {
  for (int i = 0; i < MAX_BULLETS; i++) {
    if (!bullets[i].active) {
      bullets[i].active = true;
      bullets[i].x = player.x + PLAYER_W - 1;
      bullets[i].y = player.y + PLAYER_H / 2;
      return;
    }
  }
}

// Bullets Update

void updateBullets() {
  if (millis() - lastBulletUpdate < BULLET_INTERVAL) {
    return;
  }

  lastBulletUpdate = millis();

  for (int i = 0; i < MAX_BULLETS; i++) {
    if (!bullets[i].active) continue;

    bullets[i].x += 4;

    if (bullets[i].x > 127) {
      bullets[i].active = false;
    }
  }
}

// Explosions

void createExplosion(int x, int y) {
  for (int i = 0; i < MAX_EXPLOSIONS; i++) {
    if (!explosions[i].active) {
      explosions[i].active = true;
      explosions[i].x = x;
      explosions[i].y = y;
      explosions[i].frame = 0;
      explosions[i].lastFrame = millis();
      return;
    }
  }
}

void updateExplosions() {
  for (int i = 0; i < MAX_EXPLOSIONS; i++) {
    if (!explosions[i].active) continue;

    if (millis() - explosions[i].lastFrame > 70) {
      explosions[i].lastFrame = millis();
      explosions[i].frame++;

      if (explosions[i].frame >= 4) {
        explosions[i].active = false;
      }
    }
  }
}

// Enemy Bullets

void createEnemyBullet(int x, int y, int vx, int vy) {
  for (int i = 0; i < MAX_ENEMY_BULLETS; i++) {
    if (!enemyBullets[i].active) {
      enemyBullets[i].active = true;
      enemyBullets[i].x = x;
      enemyBullets[i].y = y;
      enemyBullets[i].vx = vx;
      enemyBullets[i].vy = vy;
      return;
    }
  }
}

void updateEnemyBullets() {
  if (millis() - lastEnemyBulletUpdate < ENEMY_BULLET_INTERVAL) {
    return;
  }

  lastEnemyBulletUpdate = millis();

  for (int i = 0; i < MAX_ENEMY_BULLETS; i++) {
    if (!enemyBullets[i].active) continue;

    enemyBullets[i].x += enemyBullets[i].vx;
    enemyBullets[i].y += enemyBullets[i].vy;

    if (enemyBullets[i].x < 0 ||
        enemyBullets[i].x >= 128 ||
        enemyBullets[i].y < PLAY_TOP ||
        enemyBullets[i].y >= 64) {
      enemyBullets[i].active = false;
    }
  }
}

// Normal Enemy Spawn

void spawnEnemy() {
  for (int i = 0; i < MAX_ENEMIES; i++) {
    if (!enemies[i].active) {
      enemies[i].active = true;
      enemies[i].x = 127;
      enemies[i].y = random(16, 55);
      enemies[i].baseY = enemies[i].y;
      enemies[i].hp = 1;
      enemies[i].speed = random(1, 3);
      enemies[i].movement = random(0, 2);
      enemies[i].phase = 0;
      enemies[i].shoots = random(0, 100) < 40;
      enemies[i].lastShot = millis();
      return;
    }
  }
}

// Normal Enemies Update

void updateEnemies() {
  if (gameState != STATE_PLAYING) return;

  if (millis() - lastEnemySpawn > 900) {
    spawnEnemy();
    lastEnemySpawn = millis();
  }

  if (millis() - lastEnemyUpdate < ENEMY_INTERVAL) {
    return;
  }

  lastEnemyUpdate = millis();

  for (int i = 0; i < MAX_ENEMIES; i++) {
    if (!enemies[i].active) continue;

    enemies[i].x -= enemies[i].speed;

    if (enemies[i].movement == 1) {
      enemies[i].phase += 0.25;
      enemies[i].y = enemies[i].baseY + (int)(sin(enemies[i].phase) * 7);
      enemies[i].y = constrain(enemies[i].y, PLAY_TOP + 2, PLAY_BOTTOM - ENEMY_H);
    }

    if (enemies[i].shoots && millis() - enemies[i].lastShot > 1500) {
      createEnemyBullet(enemies[i].x, enemies[i].y + 3, -2, 0);
      enemies[i].lastShot = millis();
    }

    if (enemies[i].x < -ENEMY_W - 2) {
      enemies[i].active = false;
    }
  }
}

// Boss

void startBoss() {
  gameState = STATE_BOSS;

  for (int i = 0; i < MAX_ENEMIES; i++) {
    enemies[i].active = false;
  }

  for (int i = 0; i < MAX_ENEMY_BULLETS; i++) {
    enemyBullets[i].active = false;
  }

  boss.active = true;
  boss.x = 128;
  boss.y = 25;
  boss.maxHP = 25;
  boss.hp = boss.maxHP;
  boss.verticalDirection = 1;
  boss.charging = false;
  boss.returning = false;
  boss.lastShot = millis();
  boss.lastCharge = millis();
}

void updateBoss() {
  if (gameState != STATE_BOSS || !boss.active) {
    return;
  }

  // enter
  if (boss.x > 100 && !boss.charging && !boss.returning) {
    boss.x--;
    return;
  }

  // start charge
  if (!boss.charging && !boss.returning && millis() - boss.lastCharge > 6000) {
    boss.charging = true;
    boss.lastCharge = millis();
  }

  // charge forward
  if (boss.charging) {
    boss.x -= 3;

    if (boss.x <= 55) {
      boss.charging = false;
      boss.returning = true;
    }

    return;
  }

  // return
  if (boss.returning) {
    boss.x += 3;

    if (boss.x >= 100) {
      boss.x = 100;
      boss.returning = false;
    }

    return;
  }

  // vertical move
  boss.y += boss.verticalDirection;

  if (boss.y <= 17) {
    boss.y = 17;
    boss.verticalDirection = 1;
  }

  if (boss.y >= 42) {
    boss.y = 42;
    boss.verticalDirection = -1;
  }

  // shoot
  if (millis() - boss.lastShot > 1100) {
    int dy = 0;

    if (player.y + PLAYER_H / 2 < boss.y + BOSS_H / 2) dy = -1;
    if (player.y + PLAYER_H / 2 > boss.y + BOSS_H / 2) dy = 1;

    createEnemyBullet(boss.x, boss.y + BOSS_H / 2, -3, dy);
    boss.lastShot = millis();
  }

  // dead
  if (boss.hp <= 0) {
    boss.hp = 0;
    boss.active = false;

    createExplosion(boss.x + BOSS_W / 2, boss.y + BOSS_H / 2);

    score += 1000;
    gameState = STATE_LEVEL_CLEAR;
  }
}

// Player Damage

void damagePlayer() {
  if (player.invincible) return;

  lives--;

  createExplosion(player.x + PLAYER_W / 2, player.y + PLAYER_H / 2);

  player.invincible = true;
  player.invincibleStart = millis();

  player.x = 12;
  player.y = 32;

  for (int i = 0; i < MAX_ENEMY_BULLETS; i++) {
    enemyBullets[i].active = false;
  }

  if (lives <= 0) {
    lives = 0;
    gameState = STATE_GAME_OVER;
  }
}

// Collision

bool rectHit(
  int ax, int ay, int aw, int ah,
  int bx, int by, int bw, int bh
) {
  return (
    ax < bx + bw &&
    ax + aw > bx &&
    ay < by + bh &&
    ay + ah > by
  );
}

void checkCollisions() {

  // bullet vs normal enemy
  for (int b = 0; b < MAX_BULLETS; b++) {
    if (!bullets[b].active) continue;

    for (int e = 0; e < MAX_ENEMIES; e++) {
      if (!enemies[e].active) continue;

      if (rectHit(
            bullets[b].x, bullets[b].y, 4, 1,
            enemies[e].x, enemies[e].y, ENEMY_W, ENEMY_H
          )) {

        bullets[b].active = false;
        enemies[e].hp--;

        if (enemies[e].hp <= 0) {
          createExplosion(enemies[e].x + ENEMY_W / 2, enemies[e].y + ENEMY_H / 2);
          enemies[e].active = false;
          score += 100;
        }

        break;
      }
    }
  }

  // bullet vs boss
  if (boss.active) {
    for (int b = 0; b < MAX_BULLETS; b++) {
      if (!bullets[b].active) continue;

      if (rectHit(
            bullets[b].x, bullets[b].y, 4, 1,
            boss.x, boss.y, BOSS_W, BOSS_H
          )) {

        bullets[b].active = false;
        boss.hp--;
        createExplosion(bullets[b].x, bullets[b].y);
      }
    }
  }

  // enemy bullet vs player
  for (int i = 0; i < MAX_ENEMY_BULLETS; i++) {
    if (!enemyBullets[i].active) continue;

    if (rectHit(
          enemyBullets[i].x, enemyBullets[i].y, 2, 2,
          player.x + 1, player.y + 1, PLAYER_W - 2, PLAYER_H - 2
        )) {

      enemyBullets[i].active = false;
      damagePlayer();
      return;
    }
  }

  // enemy body vs player
  for (int i = 0; i < MAX_ENEMIES; i++) {
    if (!enemies[i].active) continue;

    if (rectHit(
          player.x + 1, player.y + 1, PLAYER_W - 2, PLAYER_H - 2,
          enemies[i].x, enemies[i].y, ENEMY_W, ENEMY_H
        )) {

      enemies[i].active = false;
      damagePlayer();
      return;
    }
  }

  // boss body vs player
  if (boss.active) {
    if (rectHit(
          player.x + 1, player.y + 1, PLAYER_W - 2, PLAYER_H - 2,
          boss.x, boss.y, BOSS_W, BOSS_H
        )) {

      damagePlayer();
      return;
    }
  }
}

// Starfield

void updateStars() {
  if (millis() - lastStarUpdate < STAR_INTERVAL) {
    return;
  }

  lastStarUpdate = millis();

  for (int i = 0; i < MAX_STARS; i++) {
    stars[i].x -= stars[i].speed;

    if (stars[i].x < 0) {
      stars[i].x = 127;
      stars[i].y = random(PLAY_TOP + 2, PLAY_BOTTOM);
      stars[i].speed = random(1, 3);
    }
  }
}

// Draw Background

void drawBackground() {
  for (int i = 0; i < MAX_STARS; i++) {
    u8g2.drawPixel(stars[i].x, stars[i].y);
  }

  static int terrainOffset = 0;

  terrainOffset--;

  if (terrainOffset <= -16) {
    terrainOffset = 0;
  }

  for (int x = terrainOffset; x < 128; x += 16) {
    u8g2.drawLine(x, 63, x + 4, 59);
    u8g2.drawLine(x + 4, 59, x + 8, 61);
    u8g2.drawLine(x + 8, 61, x + 12, 57);
    u8g2.drawLine(x + 12, 57, x + 16, 63);
  }
}

// Draw Player

void drawPlayerShip(int xPos, int yPos) {
  for (int y = 0; y < PLAYER_H; y++) {
    for (int x = 0; x < PLAYER_W; x++) {
      if (playerShip[y][x] == '#') {
        u8g2.drawPixel(xPos + x, yPos + y);
      }
    }
  }
}

void drawPlayer() {
  if (player.invincible) {
    if ((millis() / 100) % 2 == 0) {
      return;
    }
  }

  drawPlayerShip(player.x, player.y);

  // engine blink
  if ((millis() / 80) % 2 == 0) {
    u8g2.drawPixel(player.x - 1, player.y + PLAYER_H / 2);
  }
}

// Draw Bullets

void drawBullets() {
  for (int i = 0; i < MAX_BULLETS; i++) {
    if (!bullets[i].active) continue;

    u8g2.drawLine(
      bullets[i].x,
      bullets[i].y,
      bullets[i].x + 3,
      bullets[i].y
    );
  }
}

// Draw Normal Enemies

void drawEnemies() {
  for (int i = 0; i < MAX_ENEMIES; i++) {
    if (!enemies[i].active) continue;

    u8g2.drawXBMP(
      enemies[i].x,
      enemies[i].y,
      ENEMY_W,
      ENEMY_H,
      enemySprite
    );
  }
}

// Draw Boss

void drawBossMonster(int xPos, int yPos) {
  for (int y = 0; y < BOSS_H; y++) {
    for (int x = 0; x < BOSS_W; x++) {
      if (bossMonster[y][x] == '#') {
        u8g2.drawPixel(xPos + x, yPos + y);
      }
    }
  }
}

void drawBoss() {
  if (!boss.active) return;

  drawBossMonster(boss.x, boss.y);
}

// Draw Enemy Bullets

void drawEnemyBullets() {
  for (int i = 0; i < MAX_ENEMY_BULLETS; i++) {
    if (!enemyBullets[i].active) continue;

    u8g2.drawBox(
      enemyBullets[i].x,
      enemyBullets[i].y,
      2,
      2
    );
  }
}

// Draw Explosions

void drawExplosions() {
  for (int i = 0; i < MAX_EXPLOSIONS; i++) {
    if (!explosions[i].active) continue;

    int r = explosions[i].frame + 1;

    u8g2.drawCircle(explosions[i].x, explosions[i].y, r);

    u8g2.drawPixel(explosions[i].x - r - 1, explosions[i].y);
    u8g2.drawPixel(explosions[i].x + r + 1, explosions[i].y);
    u8g2.drawPixel(explosions[i].x, explosions[i].y - r - 1);
    u8g2.drawPixel(explosions[i].x, explosions[i].y + r + 1);
  }
}

// HUD

void drawHUD() {
  char text[20];

  u8g2.setFont(u8g2_font_5x8_tf);

  snprintf(text, sizeof(text), "L%d", lives);
  u8g2.drawStr(1, 8, text);

  snprintf(text, sizeof(text), "%05lu", score);
  u8g2.drawStr(98, 8, text);

  u8g2.drawLine(0, 10, 127, 10);
}

// Boss Health

void drawBossHealth() {
  if (!boss.active) return;

  int hpWidth = map(boss.hp, 0, boss.maxHP, 0, 48);
  hpWidth = constrain(hpWidth, 0, 48);

  u8g2.drawFrame(39, 12, 50, 5);

  if (hpWidth > 0) {
    u8g2.drawBox(40, 13, hpWidth, 3);
  }
}

// Pause

void drawPause() {
  u8g2.setDrawColor(0);
  u8g2.drawBox(34, 23, 60, 18);
  u8g2.setDrawColor(1);

  u8g2.drawFrame(34, 23, 60, 18);
  u8g2.setFont(u8g2_font_6x12_tf);
  u8g2.drawStr(46, 36, "PAUSE");
}

// Game Over

void drawGameOver() {
  u8g2.setFont(u8g2_font_6x12_tf);
  u8g2.drawStr(34, 29, "GAME OVER");

  u8g2.setFont(u8g2_font_5x8_tf);
  u8g2.drawStr(28, 43, "Q1 RESTART");
}

// Level Clear

void drawLevelClear() {
  u8g2.setFont(u8g2_font_6x12_tf);
  u8g2.drawStr(27, 29, "LEVEL CLEAR");

  u8g2.setFont(u8g2_font_5x8_tf);
  u8g2.drawStr(28, 43, "Q1 RESTART");
}

// Render Helpers

void renderPlayfield() {
  drawBackground();
  drawPlayer();
  drawBullets();
  drawEnemies();
  drawEnemyBullets();
  drawBoss();
  drawExplosions();
  drawHUD();

  if (boss.active) {
    drawBossHealth();
  }
}

void renderGame() {
  u8g2.clearBuffer();

  if (gameState == STATE_TITLE) {
    drawLogo();
  }
  else if (gameState == STATE_PLAYING || gameState == STATE_BOSS) {
    renderPlayfield();
  }
  else if (gameState == STATE_PAUSED) {
    renderPlayfield();
    drawPause();
  }
  else if (gameState == STATE_GAME_OVER) {
    drawExplosions();
    drawGameOver();
  }
  else if (gameState == STATE_LEVEL_CLEAR) {
    drawExplosions();
    drawLevelClear();
  }

  u8g2.sendBuffer();
}

// Setup

void setup() {
  Serial.begin(115200);

  Wire.begin();
  u8g2.begin();

  randomSeed(micros());

  gameState = STATE_TITLE;
  renderGame();
}

// Loop

void loop() {
  updateTouch();

  // TITLE
  if (gameState == STATE_TITLE) {
    if (touchPressed(T_Q1)) {
      resetGame();
    }

    renderGame();
    delay(10);
    return;
  }

  // PAUSED
  if (gameState == STATE_PAUSED) {
    if (touchPressed(T_Q2)) {
      gameState = stateBeforePause;
    }

    renderGame();
    delay(10);
    return;
  }

  // GAME OVER / LEVEL CLEAR
  if (gameState == STATE_GAME_OVER || gameState == STATE_LEVEL_CLEAR) {
  updateExplosions();

  if (touchPressed(T_Q1)) {

    gameState = STATE_TITLE;

    // optional: clear active objects
    for (int i = 0; i < MAX_BULLETS; i++) {
      bullets[i].active = false;
    }

    for (int i = 0; i < MAX_ENEMY_BULLETS; i++) {
      enemyBullets[i].active = false;
    }

    for (int i = 0; i < MAX_ENEMIES; i++) {
      enemies[i].active = false;
    }

    for (int i = 0; i < MAX_EXPLOSIONS; i++) {
      explosions[i].active = false;
    }

    boss.active = false;
  }

  renderGame();
  delay(10);
  return;
}
  // Q2 pause
  if (touchPressed(T_Q2)) {
    stateBeforePause = gameState;
    gameState = STATE_PAUSED;

    renderGame();
    delay(10);
    return;
  }

  // Q1 fire
  if (touchPressed(T_Q1)) {
    fireBullet();
  }

  // updates
  updatePlayer();
  updateBullets();
  updateEnemyBullets();
  updateStars();
  updateExplosions();

  // normal level
  if (gameState == STATE_PLAYING) {
    updateEnemies();

    if (score >= BOSS_SCORE) {
      startBoss();
    }
  }

  // boss
  if (gameState == STATE_BOSS) {
    updateBoss();
  }

  // collisions
  checkCollisions();

  // render
  renderGame();

  delay(10);
}