Class Dependency Ripple: SOLID Coupling & Change-Impact Simulator

This simulation puts a small object-oriented codebase in front of you as a 3D dependency graph: amber wireframe nodes are interfaces, solid nodes are concrete classes, and every edge is a real "depends on" relationship. Instead of a generic software-development-lifecycle overview, it narrows in on one concrete, measurable mechanic from object-oriented design — coupling and change propagation — using Robert C. Martin's Instability (I) and Abstractness (A) metrics from the Stable Dependencies and Dependency Inversion principles (two of the five SOLID principles). Pick any class and trigger "Modify" to watch a breadth-first search ripple backward through every class that transitively depends on it, reporting the exact blast radius of that change. Inject a tight coupling edge to see the graph's average instability and "distance from the main sequence" get worse in real time, or extract an interface to watch a class in the "zone of pain" move back toward the healthy D ≈ 0 region — the same trade-off every refactoring decision in a real codebase has to make.