This research report presents the results of a STEM summer program on robotics and game design. The program was part of a three-year study funded by the National Science Foundation. Children in grades four through six participated in a two-week summer camp in 2015 to learn STEM by engaging in LEGO® EV3 robotics and computer-based games using Scalable Game Design. Twentyeight students participated in the study that took place in a small urban community in the Rocky Mountain West. This paper reports on the results of this part of the study, specifically, how children's computational thinking skills developed and how their self-efficacy in technology, attitude toward engineering and technology, and 21st century skills changed as a result of their participation. [For the complete proceedings, see ED583608.]