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invaders by wilkie 

# Space Invaders clone

# Create a new window for us to use
Shoes.app :width => 600, :height => 400, :resizable => false do
  background black
  
  # Create those monsters
  monsters_per_row = 10
  rows = 5
  
  @monsters = []
  @bullets = []
  
  # They have some girth that will fit on the screen
  # Remember, we have to play fair and give them room to move!
  monster_girth = self.height / monsters_per_row / 2.4
  monster_space = monster_girth * 2

  # Monsters are slow at first
  monster_movement = self.width / 600
  
  # Monsters start centered
  start_x = (self.width - monster_space * monsters_per_row) / 2
    
  # Each of them will be represented by a square
  rows.times do |y|
    monsters_per_row.times do |x|
      mx = x * monster_space + start_x
      my = y * monster_space + monster_girth*2
      @monsters << rect(mx, my, monster_girth, :fill => white)
    end
  end
  
  # The player is a square
  px = (self.width - monster_girth) / 2
  @player = rect px, self.height - monster_girth * 2, monster_girth, :fill => blue
  
  # The bullets are oval
  @bullet = oval 0, 0, 4, 7, :fill => yellow
  @bullet.hide
  
  # The player is initially at rest
  @moving = 0
  
  every 3 do
    # Find a monster to shoot at the player
    m = @monsters[rand(@monsters.size)]
    
    # Center that bullet!
    bx = m.left + monster_girth / 2 + 5
    by = m.top + monster_girth - 5
    
    # Fire!
    @bullets << oval(bx, by, 10, :fill => green)
  end
  
  @anim = animate 200 do
    change_directions = false
    
    # All of the monsters go left and right
    @monsters.each do |m|
      m.move m.left + monster_movement, m.top
      
      # Did the monster hit a wall?
      if m.left + monster_girth + monster_movement > self.width or m.left + monster_movement < 0
        change_directions = true
      end
      
      # Did the monster get to Earth?
      if m.top + monster_girth > @player.top
        @anim.stop and alert('You lose!')
        break
      end
    end
    
    # Are the monsters defeated?
    if @monsters.size == 0
      @anim.stop and alert('You win!')
    end
  
    # Move the monsters down, increase their speed, change directions!
    if change_directions
      monster_movement = -monster_movement * 1.1
      
      # Monsters go toward the player
      @monsters.each do |m|
        m.move m.left, m.top + monster_girth
      end
    end
    
    # Move the player
    @player.move @player.left + @moving, @player.top
    
    # Move bullet
    @bullet.move @bullet.left, @bullet.top - 10
    
    # Move invader bullets
    @bullets.each do |b|
      b.move b.left, b.top + 7

      # Check to see if bullet hit player or went off screen
      if b.top > @player.top
        if b.left + 5 > @player.left and b.left + 5 < @player.left + monster_girth
          # Bullet hit player
          @anim.stop and alert('You were shot!') and break
        end
        @bullets.delete b and b.hide
      end
    end
    
    # Does bullet hit monster?
    @monsters.each do |m|
      if @bullet.left + 2 > m.left and @bullet.left + 2 < m.left + monster_girth
        if @bullet.top + 3 > m.top and @bullet.top + 3 < m.top + monster_girth
          @bullet.move 0, 0 and @bullet.hide
          @monsters.delete m and m.hide
        end
      end
    end 
  end
  
  # Respond to key presses to move player and shoot
  keypress do |key|
    if key == :left
      @moving = -4
    elsif key == :right
      @moving = 4
    elsif key == " "
      @bullet.move @player.left + monster_girth / 2 - 2, @player.top
      @bullet.show
    end
  end
end