You know SOLID. You can name the Gang of Four patterns. But when someone challenges your design decision, can you explain the trade-off—or only repeat the rule? Principles you cannot articulate are principles you cannot apply. 79 principles. Zero hand-waving. Each follows the same rigorous format: a clear explanation, warning signs that reveal violations, and markers that confirm correct application. No "it depends" without explaining why. Five chapters cover: SOLID and core design principles—as trade-offs, not commandments - Components and dependencies—coupling, cohesion, and the forces that shape them - Contracts and correctness—the discipline that separates reliable code from fragile code - Clarity and readability—why good code explains itself - The complete Gang of Four catalog—when they solve problems, when they create them Reach for this book before an interview, during a design debate, or when refactoring unfamiliar code. Design Foundations is Book 1 of the Software Development Principles series. Language-agnostic. Framework-independent. Built to last. Your foundations determine everything you build on top of them. Make yours unshakeable.