"Your First Cocoa Application" in the Swift Programming: The Big Nerd Ranch Guide (2nd Ed.) e-book: If you have not already completed the silver challenge, do that first! Now that your buttons react when the app starts or stops speaking, give the user a way to know how long speaking will continue. Add an NSProgressIndicator to your interface and update it to show a rough estimate of how much speaking has been completed. For bonus points, make the progress indicator visible only when the app is speaking.