In short, the playground that I submitted this year aimed to simulate an electronic circuit. The circuit is illustrated in diagram form and is interactive. You can interact with the switch and double tap to access the value adjustment screen where you can play around with the values of both the battery and the resistor.
During creation I did tinker with an alternative circuit that included a buzzer instead of an LED. However, I ran out of time focusing on polishing various aspects of my playground book.
If you have an iPad, you can experience my Playground book by opening the appropriate playground book file in Swift Playgrounds. Alternatively, I've packaged the core functionality of the playground book into a standard Xcode playground if you would like to try it out there.
I was particularly pleased with the drawing animation that I was able to achieve.
