This book provides a multilingual introduction to Java, JavaScript, and Python, and facilitates how programmers can move from one language to the other without having to learn a new IDE. It uses the graphics, visualization, and interactive functionality of the Processing environment to provide illustrations of essential concepts for web, mobile, and console interactive programming. Each language is introduced in an independent chapter that can be approached in any order. Accessible examples are included throughout, along with "seed projects" which are intentionally incomplete code projects that motivate readers to focus on a concept while adapting the project to their own purposes.