This paper presents the Unruly Splats platform designed to promote active STEM play. We summarize design considerations that shaped its current prototype. Unruly Splats are a set of foot-sized floor buttons that light up, sense pressure, and make sounds, according to programs that learners age 6 and up create using a blocks-based programming environment on their tablets or computers. We discuss how the system works using a game in the whack-a-mole genre. The paper illustrates the ways in which programs and Splats connect, to allow for a low-barrier to entry into coding experiences while supporting a myriad of programming possibilities. We discuss the role that the “pick random number” block plays in creating challenging and collaborative experiences and conclude with observations from interactions with early users.