Real-world applications of state machines, statecharts, and the actor model in production UI code. Each case study explains the problem, the machine design, and the outcome.

• Document Editor — Version history, branching, and edit confirmation

• E-Commerce Checkout — Multi-step checkout with async validation

• Collaborative Editing — Real-time sync, conflict resolution, cursors

• Onboarding Flow — Multi-step onboarding with branching logic

• Media Player — Play, pause, buffering, seeking states