We don’t often do 15 minute challenges. But when we do we tend to try to keep them simpler.
In this case I suppose it could have gotten a little complex, but as with most topics that’s up to the artist.
Regardless though, keep in mind a ‘15 minute’ challenge still has a 15 minute submission window as well, which you are welcome to work during. Really, this is the most ‘30 minute’ the 30 minute challenge gets!
Sorry if it’s tight for you, but it is what it is. A rare thing where speed is the name of the game.