With artificial intelligence (AI) poised to transform the nature of creative media, it is especially important to design tools with the creative process in mind. While ample research demonstrates the importance of flow, playfulness, and exploration for creative tasks, these concepts are rarely considered when designing digital interfaces. My thesis develops principles for the design of intelligent and playful user interfaces through a series of concrete design tasks. I explore a number of approaches for establishing artist needs, develop digital representations that are amenable to both machine learning and user interaction, and design novel digital media that amplify, not stifle, creativity. I conclude with an informal design philosophy developed throughout this study and thoughts on how we can leverage AI to elevate human creativity.