You could stop the real-time building and compile by clicking the stop button ⏹. And the time you finish coding, just click the start button ▶️ and it will compile. For testing, if it runs slow on your XCode, you could try to airdrop or iCloud sync the file to your iPad. And it typically runs faster on an iPad.
Hope that solves your question, and good luck to your submission.
Try not to put all of your code in the .playground. You can create new .swift file in the Source folder, that would be much better. If the timeline is not running just go ahead and give Xcode a restart (close and reopen)
Hello, I got the same issue until i realized that I had to manually select each time in the Assistant Editor > Timeline > MyPlayground.playground (Timeline)
Hope it helps you!