Module Help..

[Chaosg1]

I have created a module called mask that checks if there is a colision inside a circle...
here it is:

module Mask
  
  def self.circle(x,y,r)
    bottom_x = x
    bottom_y = y
    top_x = x
    top_y = y
    loop do
    for i in -r...r
      # check the bottom half circle
      if self.passable?(bottom_x+i,bottom_y)
        bottom_y - 1 
        r - 1
        if top_y < y + r
          @bottom = true
        end
      else
        @bottom = false
      end
      # check the top half circle
      if self.passable?(top_x+i,top_y)
        top_y + 1
        r - 1
        if top_y > y+r
          @top = true
        end
      else
        @top = false
      end
      if @bottom = true and @top == true
        return true
      else return false
      end
    end
    end
  end

  
  def self.passable?(x,y)
    if $game_map.pixel_passable?(x,y,0, nil,"Tileset")
      return true
    else
      return false
    end
  end
end

But whenever I call it it does shit, nothin happens... Basicly what I want is that it checks if the is one impassable pixel inside the circle with 2*r diameter... Could you please tell me what's wrong?