A self-contained, custom implementation of gesture recognition for canvas interaction, supporting drag, pinch, scroll, wheel, move, and hover events. Implements a configurable resolver system for each gesture type with proper coordinate transformations, timeout handling, and state management. Demonstrates deep understanding of multi-touch and mouse events, and is structured as independent modules (config, engines, types) that could be extracted into a standalone gesture library with minimal adaptation.

A production-quality undo/redo stack that supports operation batching, merge strategies (replace, merge, skip), and max stack depth. Implements inverse operations and provides hooks for custom merge logic. Fully independent of the rest of the codebase — uses only TypeScript basics and is reusable in any application requiring undo/redo with compound operations.

A plugin that implements automatic graph layout using the Dagre algorithm, including order, cross-count, sort-subgraph, and feasible-tree stages. Provides animated transitions between layout states and integrates with the free-layout editor's node/line services. The algorithm and animation logic are self-contained and could be reused in any graph visualization tool, not tied to the editor's DI system.

The core form engine with a reactive model supporting fields, arrays, validation triggers, effects, and plugin-based extensions. Uses inversify for DI, but the underlying FormModel and Field abstractions are designed to be agnostic of UI framework. The ability system (setter, decorator, visibility, effect, default) demonstrates a clean separation of concerns and is reusable as a standalone reactive form solution.