Makerspaces can support educational experiences in prototyping for young learners, while physical computing platforms enable high levels of creativity and expression. However, each of these have high barriers of entry, especially for youth without prior experience. Commercial microcontrollers have become a popular tool to use when designing both basic and complex electro-mechanical devices. Block-based programming interfaces are an ideal environment to program these microcontrollers, lowering the barrier of entry for young, novice programmers. Finally, incorporating physical computing devices alongside Augmented Reality (AR) presents opportunities for shared experiences between users, leading to more engagement, which creates opportunities for social interaction, ideation, and creativity. This thesis presents the MakAR project, which aims to empower youth to design, build, and play through interactions with AR, physical prototyping, and the Internet of Things (IoT). We sought to design an interactive system with which we can (1) explore novel interactions between physical and virtual content, (2) lower the barrier to entry for young makers to design, build, and play with DIY electro-mechanical devices, and (3) engage and collaborate with one another both virtually and physically in an AR-IoT environment. Our results provide evidence to how our system enables youth, with and without prior experience with physical computing, to both engage and struggle with designing AR-IoT interactions while using our system, helps reduce the barrier to entry for young users to create complex electromechanical devices, and provides unique shared AR-IoT experiences for both novices and expert users. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]