The type or namespace name ‘App’ could not be found. Are you missing an assembly reference?

I got this error when I was trying to deploy this: https://github.com/xamarin/xamarin-forms-samples/tree/master/BugSweeper

I was able to build other Android/iOS apps that don't rely on Xamarin.Forms, so I think that's where the problem is from.

And here are some screenshots: