It's saying something about a runtime error? This is my first time exparamenting with making a game, so I have no idea how to fix this. Any help is appreciated :)
Create 2D games in JavaScript, made easier · By
You need to open the file with a text editor. Instead of double-clicking on the file, try right-click > "open file with"
Any text editor will work (for instance Notepad), but I recommend VS Code (https://code.visualstudio.com/) or Atom (https://atom.io/).