Implements a clean event propagation pattern where handlers can indicate whether they've captured an event (preventing further propagation) or let it bubble up. The Let_syntax module provides ergonomic syntax for chaining handlers while respecting capture boundaries. This is a self-contained, reusable pattern with minimal dependencies (only Core) that solves a common problem in event-driven systems.

Provides a sophisticated view system with efficient memoization (Single_memo), layout operations (vcat, hcat, zcat), and a tagging system for associating metadata with views. The memoization avoids redundant computations when view inputs haven't changed, and the tagging system allows extracting layout information post-composition. Demonstrates advanced functional programming techniques for building reusable UI components.

Contains focused, isolated modules for managing different aspects of application state: dimensions (terminal size), clock (timekeeping), and exit status. Each module encapsulates its concern with a minimal, clear API. This separation makes the system easier to reason about, test, and maintain. The pattern is broadly applicable to any stateful application and could be extracted with minimal adaptation.