Most of these overlay / walkthroughs can be accomplished by adding a subview to the main window of your application. There are some cases of edges that need to be considered, but for the most part you just need to get a link to a window with
UIWindow* keyWindow; keyWindow = [UIApplication sharedApplication].keyWindow;
Then you would add your overlay view as a subcategory with:
[keyWindow addSubview:anOverlayView]
The processing of taps to reject the overlay can be performed using a gesture recognizer.
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