Introductory computing students often receive compiler error messages, particularly related to data types, that can be difficult to understand and hurt confidence. Type inference, the process responsible for generating data type errors, is currently hidden within the compiler, and introducing it to students in a structured way could help them better trace program behavior and explain their errors. We introduce Type Circuits, an online type inference visualizer for introductory students that can generate printable small-group activities in multiple programming languages. We piloted these activities in a high school classroom and found they were engaging and show promise as a future assessment tool. Future work will evaluate Type Circuits at a larger scale.