diff --git a/lib/renderer/g_buffer.rb b/lib/renderer/g_buffer.rb
index da0f1f8..5388caf 100644
--- a/lib/renderer/g_buffer.rb
+++ b/lib/renderer/g_buffer.rb
@@ -151,15 +151,13 @@ class IMICFPS
     end
 
     def clean_up
-      glDeleteFramebuffers(@framebuffer)
+      glDeleteFramebuffers(1, [@framebuffer].pack("L"))
 
-      @textures.values.each do |id|
-        glDeleteTextures(id)
-      end
+      glDeleteTextures(@textures.values.size, @textures.values.pack("L*"))
 
-      glDeleteBuffers(@positions_buffer_id)
-      glDeleteBuffers(@uvs_buffer_id)
-      glDeleteVertexArrays(@screen_vbo)
+      glDeleteBuffers(2, [@positions_buffer_id, @uvs_buffer_id].pack("L*"))
+      glDeleteVertexArrays(1, [@screen_vbo].pack("L"))
+      gl_error?
     end
   end
 end
\ No newline at end of file
diff --git a/lib/renderer/opengl_renderer.rb b/lib/renderer/opengl_renderer.rb
index 2eb69c2..01f9e0b 100644
--- a/lib/renderer/opengl_renderer.rb
+++ b/lib/renderer/opengl_renderer.rb
@@ -8,8 +8,15 @@ class IMICFPS
       @g_buffer = GBuffer.new
     end
 
+    def canvas_size_changed
+      @g_buffer.unbind_framebuffer
+      @g_buffer.clean_up
+
+      @g_buffer = GBuffer.new
+    end
+
     def render(camera, lights, entities)
-      if Shader.available?("default")
+      if Shader.available?("default") && Shader.available?("render_screen")
         @g_buffer.bind_for_writing
         gl_error?
 
diff --git a/lib/renderer/renderer.rb b/lib/renderer/renderer.rb
index 66b213e..31a30d5 100644
--- a/lib/renderer/renderer.rb
+++ b/lib/renderer/renderer.rb
@@ -28,6 +28,10 @@ class IMICFPS
       @opengl_renderer.render(camera, lights, entities)
     end
 
+    def canvas_size_changed
+      @opengl_renderer.canvas_size_changed
+    end
+
     def finalize # cleanup
     end
   end
diff --git a/lib/window.rb b/lib/window.rb
index eb64235..a416f4d 100644
--- a/lib/window.rb
+++ b/lib/window.rb
@@ -27,6 +27,8 @@ class IMICFPS
       @renderer.preload_default_shaders
       @scene = TurnTableScene.new
 
+      @canvas_size = Vector.new(self.width, self.height)
+
       at_exit do
         @config.save!
       end
@@ -45,6 +47,12 @@ class IMICFPS
 
       @console.draw if @show_console
       draw_cursor if needs_cursor
+
+      _canvas_size = Vector.new(self.width, self.height)
+      if @canvas_size != _canvas_size
+        @renderer.canvas_size_changed
+        @canvas_size = _canvas_size
+      end
     end
 
     def draw_cursor