Please tell me how to make it so that the size of the main window can not be changed?
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You cannot do that. The best you can do is make your game UI scale automatically to adjust to the new window size.
https://drive.google.com/file/d/0B-xiqK ... sp=sharing
If you are going to export it as NW.js (executable file to be run on desktop operating systems), you will have an option when exporting.