👾 Flutter Retro Game Series: Part 2 — Building Space Invaders with AI-like Enemies & Retro FX

🚀 The Battle Continues: From Tetris to Space Invaders

Welcome to Part 2 of the Flutter Retro Game Series. After diving deep into matrix logic and falling blocks in Tetris, we’re now taking to the skies with a classic: Space Invaders.

This game adds a whole new dimension — literally. With dynamic enemies, animated backgrounds, auto-shooting mechanics, and layered difficulty, this project pushes Flutter’s widget system to new heights.

📺 Watch the gameplay demo:

[embed]

👾 Game Features at a Glance

The game includes:

• 🚀 Smooth player spaceship movement
• 👾 Enemies with types, health, and behavior
• 💥 Bullet collision system
• 🌀 Animated starfield + galaxy effects
• 🔄 Leveling and increasing difficulty
• ❤️ Lives, score, and game state management
• 🎮 Responsive gesture-based controls

👨‍🚀 Player Control — Pan Gestures

We use GestureDetector to move the spaceship:

void _handlePanUpdate(DragUpdateDetails details) {
  final deltaX = details.delta.dx;
  final newX = _gameState.playerPosition.dx + deltaX * 4;

  _gameState = _gameState.copyWith(
    playerPosition: Offset(
      newX.clamp(20, _gameSize.width - 20), 
      _gameState.playerPosition.dy,
    ),
  );
}

Key Points:

• Multiplied deltaX for faster movement
• clamp keeps the ship on-screen
• Players can only move horizontally

💥 Bullet System — Auto Fire Every 300ms

Bullets are created from the ship’s current position:

void _autoShoot() {
  if (!_canShoot()) return;

  _lastShot = DateTime.now();
  final bullet = Bullet(
    position: Offset(
      _gameState.playerPosition.dx,
      _gameState.playerPosition.dy - 10,
    ),
    velocity: Offset(0, -1),
  );

  _gameState = _gameState.copyWith(
    bullets: [..._gameState.bullets, bullet],
  );
}

Fun fact: We trigger HapticFeedback.lightImpact() on every shot for tactile feel.

👾 Spawning Enemies — Random with Types

Every few seconds, we add new enemies with unique behavior:

void _spawnEnemy() {
  final random = Random();
  final x = random.nextDouble() * (_gameSize.width - 40) + 20;
  final enemyType = EnemyType.values[random.nextInt(3)];

  final enemy = Enemy(
    position: Offset(x, -20),
    velocity: Offset((random.nextDouble() - 0.5) * 50, 0),
    type: enemyType,
    health: enemyType.health,
  );

  _gameState = _gameState.copyWith(
    enemies: [..._gameState.enemies, enemy],
  );
}

Enemy Types:

enum EnemyType {
  scout(health: 1, points: 10),
  fighter(health: 2, points: 25),
  bomber(health: 3, points: 50);
}

• Scouts are weak and fast
• Fighters take two hits
• Bombers are tougher, slow-moving threats

🧠 Collision Logic — Bullet vs. Enemy

We check for collisions on every game tick:

bool _isColliding(Offset a, Offset b, double radius) {
  return (a - b).distance < radius;
}

Enemy Damage Handling:

for (final bullet in bullets) {
  for (final enemy in enemies) {
    if (_isColliding(bullet.position, enemy.position, 20)) {
      enemy.health--;
      if (enemy.health <= 0) {
        enemies.remove(enemy);
        score += enemy.type.points;
      }
    }
  }
}

🌌 Rendering with CustomPainter

We render everything manually using Canvas. Here’s how the player is drawn:

void _drawPlayer(Canvas canvas, Offset position) {
  final paint = Paint()..color = Colors.cyan;
  final path = Path()
    ..moveTo(position.dx, position.dy - 15)
    ..lineTo(position.dx - 15, position.dy + 15)
    ..lineTo(position.dx + 15, position.dy + 15)
    ..close();

  canvas.drawPath(path, paint);
}

📈 Level Progression

Every 30 seconds, we bump the difficulty.

void _nextLevel() {
  _gameState = _gameState.copyWith(level: _gameState.level + 1);
}

This affects enemy speed dynamically:

enemy.position.dy += (_enemySpeed + _gameState.level * 10) * deltaTime;

🎮 Try It Live!

🚀 **Play the Game in Your Browser** No install required — jump in and defend the galaxy right from your browser!

Clone the repo, open the project, and shoot some aliens! Customize the game loop, enemy types, or add power-ups.

🔗 GitHub Repo

This game proves that Flutter can do real-time game mechanics, render dynamic visuals, and support rich interactions — all without a game engine.

More games are coming in this retro series — stay tuned!

📬 Stay Connected

Got questions? Ideas? PRs? Please leave a comment or reach out to me on GitHub.

Would you like to continue this format for Part 3, or would you prefer me to help structure it as a YouTube tutorial script?