Building on foundations introduced in CS 2100, examines program design at increasing scales of complexity. Reviews abstraction, encapsulation, inheritance, and interfaces in statically-typed object-oriented languages. Presents a comparative approach to software design patterns and paradigms, including object-oriented and functional programming. Fosters a deeper understanding of the principles of program design, including interface design, test-driven development, graphical design notations, reusable software components, and open-source ecosystems. Illustrates the impact of design-time decisions on software correctness, including accessibility, changeability, performance, reusability and privacy. Students collaborate throughout the semester to design and implement a large software project.