Very fun spatial challenge!
These challenges seem to be coming in the week after I do something very similar. Love utilizing the spatial tools! See spoiler for details.
Tried two approaches... one using a sine function to model the 'altered' portion of each moon phase, and a second using the spatial process tool to 'cut out' the proper shape for each phase. approach 2 was closer to the provided output for the challenge.
Tricky but fun! Find my video solution here: https://www.youtube.com/watch?v=BEyYaFqrsww&list=PL18SpOXDj-KMUD4YwWC5vZaUsIa7drxNZ&index=55