diff --git a/examples/basics/circle_thickness.rb b/examples/basics/circle_thickness.rb
index bf4bb51..5f89195 100644
--- a/examples/basics/circle_thickness.rb
+++ b/examples/basics/circle_thickness.rb
@@ -10,7 +10,7 @@
 green = GD::Color.rgb(40,180,80)
 
 # Fondo
-img.filled_rectangle(0,0,SIZE,SIZE, white)
+img.fill(0,0,SIZE,SIZE, white)
 
 # Círculo fino (por defecto thickness = 1)
 img.circle(200,200,150, red)
diff --git a/examples/invaders/main.rb b/examples/invaders/main.rb
new file mode 100644
index 0000000..7b49417
--- /dev/null
+++ b/examples/invaders/main.rb
@@ -0,0 +1,376 @@
+require 'gd'
+
+# ═══════════════════════════════════════════════════════════════════════════
+# Space Invaders Animated GIF Generator using ruby-libgd
+# 
+# Generates an animated GIF of a simple Space Invaders game
+# Pure Ruby, no external processes, using ruby-libgd's native GIF support
+# ═══════════════════════════════════════════════════════════════════════════
+
+class SpaceInvadersGame
+  WIDTH = 400
+  HEIGHT = 300
+  FPS = 10
+  FRAMES = 60
+
+  def initialize(output_file = "space_invaders.gif")
+    @output_file = output_file
+    @gif = nil
+    @player_x = WIDTH / 2 - 10
+    @enemies = []
+    @bullets = []
+    @score = 0
+    @frame_count = 0
+    @direction = 1  # 1 for right, -1 for left
+    
+    initialize_enemies
+  end
+
+  # ───────────────────────────────────────────────────────────────────────
+  # Initialize enemy positions
+  # ───────────────────────────────────────────────────────────────────────
+  def initialize_enemies
+    @enemies = []
+    # 3 rows of enemies
+    (0..2).each do |row|
+      (0..4).each do |col|
+        @enemies << {
+          x: 40 + (col * 60),
+          y: 40 + (row * 40),
+          width: 20,
+          height: 20,
+          alive: true
+        }
+      end
+    end
+  end
+
+  # ───────────────────────────────────────────────────────────────────────
+  # Generate the animated GIF
+  # ───────────────────────────────────────────────────────────────────────
+  def generate
+    puts "🎮 Generating Space Invaders GIF..."
+    puts "   Size: #{WIDTH}x#{HEIGHT}, Frames: #{FRAMES}, FPS: #{FPS}"
+
+    FRAMES.times do |frame|
+      @frame_count = frame
+      update_game_state
+      img = render_frame
+      add_frame_to_gif(img)
+    end
+
+    close_gif
+    puts "GIF saved to: #{@output_file}"
+    puts "   Size: #{File.size(@output_file) / 1024}KB"
+  end
+
+  # ───────────────────────────────────────────────────────────────────────
+  # Update game state for this frame
+  # ───────────────────────────────────────────────────────────────────────
+  def update_game_state
+    # Move enemies left and right
+    move_enemies
+    
+    # Player moves with sin wave for smooth motion
+    @player_x = (WIDTH / 2) + (Math.sin(@frame_count * 0.3) * 80).to_i
+    @player_x = [@player_x, 0].max
+    @player_x = [@player_x, WIDTH - 20].min
+
+    # Enemies shoot randomly
+    if rand < 0.15
+      enemy = @enemies.sample
+      if enemy && enemy[:alive]
+        @bullets << {
+          x: enemy[:x] + 10,
+          y: enemy[:y] + 20,
+          enemy_bullet: true
+        }
+      end
+    end
+
+    # Player shoots
+    if @frame_count % 8 == 0
+      @bullets << {
+        x: @player_x + 10,
+        y: HEIGHT - 40,
+        enemy_bullet: false
+      }
+    end
+
+    # Update bullet positions
+    @bullets.each do |bullet|
+      if bullet[:enemy_bullet]
+        bullet[:y] += 5
+      else
+        bullet[:y] -= 7
+      end
+    end
+
+    # Remove bullets that are off-screen
+    @bullets.reject! { |b| b[:y] < 0 || b[:y] > HEIGHT }
+
+    # Check collisions
+    check_collisions
+
+    # Move enemies down and change direction at edges
+    if @frame_count % 3 == 0
+      @enemies.each do |enemy|
+        next unless enemy[:alive]
+        enemy[:x] += @direction * 8
+      end
+
+      # Change direction if any enemy hits the edge
+      if @enemies.any? { |e| e[:alive] && (e[:x] < 10 || e[:x] > WIDTH - 30) }
+        @direction *= -1
+      end
+    end
+
+    # Remove dead enemies
+    @enemies.reject! { |e| !e[:alive] }
+
+    # Reset if all enemies defeated
+    if @enemies.empty?
+      @score += 100
+      initialize_enemies
+    end
+  end
+
+  # ───────────────────────────────────────────────────────────────────────
+  # Check collisions between bullets and enemies/player
+  # ───────────────────────────────────────────────────────────────────────
+  def check_collisions
+    @bullets.each do |bullet|
+      if !bullet[:enemy_bullet]
+        # Player bullet hits enemy
+        @enemies.each do |enemy|
+          next unless enemy[:alive]
+          if collide?(bullet, enemy)
+            enemy[:alive] = false
+            @score += 10
+            @bullets.delete(bullet)
+            break
+          end
+        end
+      else
+        # Enemy bullet hits player
+        if collide?(bullet, { x: @player_x, y: HEIGHT - 30, width: 20, height: 20 })
+          @bullets.delete(bullet)
+        end
+      end
+    end
+  end
+
+  # ───────────────────────────────────────────────────────────────────────
+  # Simple collision detection
+  # ───────────────────────────────────────────────────────────────────────
+  def collide?(bullet, obj)
+    bullet[:x] > obj[:x] &&
+      bullet[:x] < obj[:x] + (obj[:width] || 20) &&
+      bullet[:y] > obj[:y] &&
+      bullet[:y] < obj[:y] + (obj[:height] || 20)
+  end
+
+  # ───────────────────────────────────────────────────────────────────────
+  # Move enemies (horizontal wave pattern)
+  # ───────────────────────────────────────────────────────────────────────
+  def move_enemies
+    # Enemies move in a wave pattern (already handled in update_game_state)
+  end
+
+  # ───────────────────────────────────────────────────────────────────────
+  # Render a frame
+  # ───────────────────────────────────────────────────────────────────────
+  def render_frame
+    img = GD::Image.new(WIDTH, HEIGHT)
+    
+    # Fill background with black
+    black = [0, 0, 0]
+    white = [255, 255, 255]
+    green = [0, 255, 0]
+    red = [255, 0, 0]
+    cyan = [0, 255, 255]
+    yellow = [255, 255, 0]
+
+    img.fill(black)
+
+    # Draw stars (background)
+    draw_stars(img, white)
+
+    # Draw enemies
+    @enemies.each do |enemy|
+      draw_enemy(img, enemy, green)
+    end
+
+    # Draw player
+    draw_player(img, @player_x, HEIGHT - 30, cyan)
+
+    # Draw bullets
+    @bullets.each do |bullet|
+      color = bullet[:enemy_bullet] ? red : yellow
+      img.filled_circle(bullet[:x], bullet[:y], 2, color)
+    end
+
+    # Draw score
+    draw_text(img, "SCORE: #{@score}", 10, 10, white)
+    draw_text(img, "ENEMIES: #{@enemies.length}", 10, 25, white)
+    draw_text(img, "FRAME: #{@frame_count}/#{FRAMES}", 10, 40, white)
+
+    img
+  end
+
+  # ───────────────────────────────────────────────────────────────────────
+  # Draw a simple enemy sprite
+  # ───────────────────────────────────────────────────────────────────────
+  def draw_enemy(img, enemy, color)
+    x = enemy[:x].to_i
+    y = enemy[:y].to_i
+    
+    # Draw enemy as a rectangle with a simple pattern
+    img.filled_rectangle(x, y, x + 20, y + 15, color)
+    
+    # Eyes
+    img.filled_rectangle(x + 4, y + 2, x + 6, y + 4, [0, 0, 0])
+    img.filled_rectangle(x + 14, y + 2, x + 16, y + 4, [0, 0, 0])
+  end
+
+  # ───────────────────────────────────────────────────────────────────────
+  # Draw player sprite
+  # ───────────────────────────────────────────────────────────────────────
+  def draw_player(img, x, y, color)
+    x = x.to_i
+    y = y.to_i
+    
+    # Draw player as a triangle (spaceship)
+    # Base
+    img.filled_rectangle(x, y + 15, x + 20, y + 20, color)
+    
+    # Cockpit
+    img.filled_rectangle(x + 7, y + 5, x + 13, y + 15, color)
+    
+    # Engine glow (blinking)
+    if @frame_count % 4 < 2
+      img.filled_rectangle(x + 5, y + 18, x + 8, y + 20, [255, 100, 0])
+      img.filled_rectangle(x + 12, y + 18, x + 15, y + 20, [255, 100, 0])
+    end
+  end
+
+  # ───────────────────────────────────────────────────────────────────────
+  # Draw animated stars in background
+  # ───────────────────────────────────────────────────────────────────────
+  def draw_stars(img, color)
+    # Use frame count to create twinkling effect
+    seed = @frame_count
+    15.times do |i|
+      x = (i * 27 + seed * 5) % WIDTH
+      y = (i * 19 + seed * 3) % HEIGHT
+      brightness = (Math.sin(seed * 0.1 + i) * 100 + 155).to_i
+      star_color = [brightness, brightness, brightness]
+      img.filled_circle(x, y, 1, star_color)
+    end
+  end
+
+  # ───────────────────────────────────────────────────────────────────────
+  # Draw text on image
+  # ───────────────────────────────────────────────────────────────────────
+  def draw_text(img, text, x, y, color)
+    # Simple text rendering using small rectangles (pixel art)
+    # For now, just use a basic placeholder
+    # In production, you'd use img.text() with a TTF font
+  end
+
+  # ───────────────────────────────────────────────────────────────────────
+  # Add frame to GIF (using ruby-libgd's native GIF support)
+  # ───────────────────────────────────────────────────────────────────────
+  def add_frame_to_gif(img)
+    if @frame_count == 0
+      # Create GIF on first frame
+      @gif = GD::Gif.new(@output_file, loop: true)
+    end
+
+    # Add frame with delay
+    delay = (1000 / FPS / 10).to_i  # Convert to centiseconds
+    @gif.add_frame(img, delay: [delay, 1].max)  # Minimum 1 centisecond
+  end
+
+  # ───────────────────────────────────────────────────────────────────────
+  # Close and save the GIF
+  # ───────────────────────────────────────────────────────────────────────
+  def close_gif
+    @gif.close if @gif
+  end
+end
+
+# ═══════════════════════════════════════════════════════════════════════════
+# RUN THE GAME
+# ═══════════════════════════════════════════════════════════════════════════
+
+if __FILE__ == $0
+  puts "🎮 Space Invaders GIF Generator"
+  puts "================================"
+  puts ""
+  
+  game = SpaceInvadersGame.new("space_invaders.gif")
+  game.generate
+  
+  puts ""
+  puts "- Play the GIF to see the game in action!"
+  puts "- Features:"
+  puts "   * Animated enemies (wave pattern)"
+  puts "   * Player movement (sin wave)"
+  puts "   * Collision detection"
+  puts "   * Scoring system"
+  puts "   * Enemy bullets vs player bullets"
+  puts "   * Twinkling stars background"
+  puts "   * 100% ruby-libgd (no external processes)"
+  puts ""
+end
+
+# ═══════════════════════════════════════════════════════════════════════════
+# ALTERNATIVE: SIMPLER VERSION (If you want to start small)
+# ═══════════════════════════════════════════════════════════════════════════
+
+class SimpleSpaceInvaders
+  def self.generate
+    puts "🎮 Generating Simple Space Invaders..."
+    
+    gif = GD::Gif.new("simple_space_invaders.gif", loop: true)
+    
+    # Generate 30 frames of simple animation
+    30.times do |frame|
+      img = GD::Image.new(300, 200)
+      
+      # Background
+      img.fill([0, 0, 50])  # Dark blue
+      
+      # Enemy (moves left and right)
+      enemy_x = 100 + (Math.sin(frame * 0.2) * 80).to_i
+      img.filled_rectangle(enemy_x, 50, enemy_x + 30, 80, [0, 255, 0])
+      
+      # Player (at bottom)
+      player_x = 130 + (Math.sin(frame * 0.1) * 40).to_i
+      img.filled_rectangle(player_x, 150, player_x + 20, 180, [0, 255, 255])
+      
+      # Bullet
+      if frame % 5 < 2
+        bullet_y = 150 - ((frame % 20) * 3)
+        img.filled_circle(player_x + 10, bullet_y, 2, [255, 255, 0])
+      end
+      
+      # Score
+      img.text("SCORE: #{frame * 10}", {
+        x: 10, y: 10,
+        size: 12,
+        color: [255, 255, 255]
+      })
+      
+      # Add frame to GIF (delay in centiseconds)
+      gif.add_frame(img, delay: 10)
+    end
+    
+    gif.close
+    puts "* Saved to: simple_space_invaders.gif"
+  end
+end
+
+# Uncomment to run the simpler version:
+# SimpleSpaceInvaders.generate
diff --git a/examples/invaders/space_invaders.gif b/examples/invaders/space_invaders.gif
new file mode 100644
index 0000000..b730c0d
Binary files /dev/null and b/examples/invaders/space_invaders.gif differ