Turing's Craft Inc is the creator of CodeLab: the web-based interactive programming exercise system for intro programming classes in Python, Java, C++, C, and C#. Codelab has been used in over 400 institutions in 20 countries and analyzed over 136,000,000 (one hundred thirty-six million) exercise submissions from more than 300,000 students. For each langauge, CodeLab has 800+ short exercises. Exercises focus on a particular programming idea or language construct. Students type in code and the system immediately judges its correctness, offering hints when the submission is incorrect. Through this process, students gain mastery over the semantics, syntax and common usage of the language elements.