Reset a playground book in Swift Playgrounds on iPad
In some playground books in Swift Playgrounds, you can reset changes you’ve made, all the way back to the starting point. This is especially useful if you want to retry a challenge you already completed or let a friend try it. You can reset the current page or all the pages in a playground.
Note: In a playground book created with the New Document button 
on the My Playgrounds screen, you can’t reset changes. You can create another blank playground by going to the My Playgrounds screen, tapping at the top, tapping New Book and then renaming the new playground. See Use and create playground books.
Reset a page in a playground book
Resetting a page removes the code changes you’ve made on the page and returns the page to its original state. In a playground that supports user modules, resetting a page resets the code in the Main Swift file on the current page (in the tab with 
at the top) but doesn’t reset the shared Swift files in the playground.
In the Swift Playgrounds app
on your iPad, go to the page you want to reset.Tap
above the coding area, then choose Start Page Over.Note: If you don’t see Start Page Over, you might be in a playground created with the New Document button
on the My Playgrounds screen, which can’t be reset.
Reset a playground book
Resetting a playground book removes the code and images you’ve added and returns the playground to its original state. In a playground book that supports user modules, resetting it removes modules and files you’ve added to the playground and removes the code changes you’ve made to any of the Swift files that came with the playground book.
In the Swift Playgrounds app
on your iPad, go to the My Playgrounds screen.If you’re on the More Playgrounds screen or working in a playground book or an app playground, tap
at the top left.Tap Select near the top right.
Select the playground book you want to reset, then tap Reset at the bottom of the screen.
Note: If Reset is dimmed, you might be in a playground created with the New Document button
on the My Playgrounds screen, which can’t be reset.