Hey! I like the extension, thanks!
Please help fix the drawing on GUI
video link :
You removed the background from the room, and the game was left without a image to clear the application_surface buffer. Then you drew a sprite in the GUI, but the GUI is not affected by the application_surface, so it was not able to get the game image correctly. Draw the background sprite in the Draw Event (this way it will be on the application_surface).
Thanks :D