hey rick! sorry about the trouble! it looks like your vs code debug environment is confused. when you switch to the debug window and click play, the first time it is trying to create the launch.json file which tells vscode how to debug.
to fix this in your environment, go ahead and edit your launch.json file that gets created and have to point to 'app.js' or '/mychess/app.js'
the folder that you launch vscode from could be causing the problem...for example, if you launch vscode from c:\projects instead of c:\projects\mychess vscode thinks that your app.js file should be in the c:\projects folder but cant find it.
if this doesn't fix it please paste in your launch.json file contents and we can fix it together :)
Have any of you written apps/tools using this XAML or MCML? It seems really cool in theory but it seems like it would be really limiting....constantly looking for the right way to describe your ui/functionality.
Again, exciting in theory but I am curious to see what kind of apps come out of it.