load_bmp → load に変更したら PNG が読めた

diff --git a/lib/stylet.rb b/lib/stylet.rb
index 663bb7b..66c493e 100644
--- a/lib/stylet.rb
+++ b/lib/stylet.rb
@@ -1,3 +1,3 @@
-require_relative "stylet/version"
-require_relative "stylet/base"
-require_relative "stylet/input"
+require_relative 'stylet/version'
+require_relative 'stylet/base'
+require_relative 'stylet/input'
diff --git a/lib/stylet/config.rb b/lib/stylet/config.rb
index 093a226..eac75ad 100644
--- a/lib/stylet/config.rb
+++ b/lib/stylet/config.rb
@@ -24,7 +24,7 @@ module Stylet
     :font_bold        => false,
     :full_screen      => false,
     :screen_size      => [640, 480],
-    :background       => false,
+    :background       => true,
     :background_image => "background.bmp",
     :color_depth      => 32,
     :sound_frequency  => 44100, # SDLのデフォルトは 22050
diff --git a/lib/stylet/core.rb b/lib/stylet/core.rb
index 8928879..7a5dd51 100644
--- a/lib/stylet/core.rb
+++ b/lib/stylet/core.rb
@@ -14,8 +14,8 @@ module Stylet
     end

     def initialize
-      @init_mode = 0
-      @sdl_initialized = false
+      @init_code = 0
+      @initialized = false
     end

     def logger
@@ -23,10 +23,13 @@ module Stylet
     end

     def before_main_loop
-      return if @sdl_initialized
-      SDL.init(@init_mode)
-      logger.debug "SDL.init #{'%08x' % @init_mode}" if logger
-      @sdl_initialized = true
+      return if @initialized
+      SDL.init(@init_code)
+      logger.debug "SDL.init #{'%08x' % @init_code}" if logger
+      @initialized = true
+    end
+
+    def polling
     end

     def before_update
diff --git a/lib/stylet/draw.rb b/lib/stylet/draw.rb
index 3d29733..4e2a76e 100644
--- a/lib/stylet/draw.rb
+++ b/lib/stylet/draw.rb
@@ -10,7 +10,7 @@ module Stylet

     def initialize
       super
-      @init_mode |= SDL::INIT_VIDEO
+      @init_code |= SDL::INIT_VIDEO
     end

     def before_main_loop
@@ -32,9 +32,9 @@ module Stylet

       if Config[:background] && Config[:background_image]
         unless @backgroud_image
-          background_image = Pathname(File.expand_path(File.join(File.dirname(__FILE__), "assets", Config[:background_image])))
+          background_image = Pathname("#{__dir__}/assets/#{Config[:background_image]}")
           if background_image.exist?
-            @backgroud_image = SDL::Surface.load_bmp(background_image)
+            @backgroud_image = SDL::Surface.load_bmp(background_image.to_s)
             if false
               # これを設定すると黒色は透明色になって描画されない
               @backgroud_image.set_color_key(SDL::SRCCOLORKEY, 0)
@@ -83,6 +83,7 @@ module Stylet
     end

     def polling
+      super
       if @sdl_event = SDL::Event.poll
         case @sdl_event
         when SDL::Event::Quit # Window の [x] が押されたとき
diff --git a/lib/stylet/joystick.rb b/lib/stylet/joystick.rb
index dadc75c..b8e19d4 100644
--- a/lib/stylet/joystick.rb
+++ b/lib/stylet/joystick.rb
@@ -6,7 +6,7 @@ module Stylet

     def initialize
       super
-      @init_mode |= SDL::INIT_JOYSTICK
+      @init_code |= SDL::INIT_JOYSTICK
     end

     def before_main_loop
active_support/configure を使うようにした