Some of the most valuable skills I can takeaway from the course are the strategies for the game development and testing discussed in the textbook: Game Design Workshop: A Playcentric Approach to Creating Innovative Games by Tracey Fullerton. One of these skills is the art of play-testing and an understanding of its importance. Aside from actually testing the game and making sure that it's ultimately fun, the feedback obtained from players is extremely important to the development of the game. In fact several ideas that were added to Recess Rabbit Rumble were suggested and implemented after the first release.
Therefore getting this feedback early is important encase there are changes that need to be made to the games mechanics; while they aren't always necessarily large, any problem is better to be caught early. Prototyping is the easiest way to develop and iterate on the core mechanics of a game idea without investing too much time in creating a complete playable demo.
The MDA (Mechanic, Dynamic, and Aesthetic) design philosophy is something else that I will take away from the course. It's an interesting take on game design, and at the very least for me it's a more formal way to design a game. I will almost certainly continue to pursue game ideas that occur to me on a whim but having an idea of how I can break down the parts of a game and help to improve all of them is a huge plus.