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+# CLAUDE.md
+
+Guide for AI assistants working on the function-plot codebase.
+
+## Project Overview
+
+**function-plot** is a TypeScript/JavaScript library for rendering interactive 2D mathematical function plots using D3.js. It supports multiple function types (linear, parametric, implicit, polar, points, vectors) and uses interval arithmetic for pixel-perfect rendering.
+
+- **Version:** 1.22.7
+- **License:** MIT
+- **Author:** Mauricio Poppe
+
+## Quick Reference Commands
+
+```bash
+# Install dependencies
+npm install
+
+# Run tests
+npm test
+
+# Development server
+npm start
+
+# Full build (webpack bundle + type declarations + site copy)
+npm run build
+
+# Individual build steps
+npm run build:webpack   # Webpack UMD bundle → dist/function-plot.js
+npm run build:types     # TypeScript declarations → dist/
+
+# Generate API docs
+npm run docs
+
+# Storybook
+npm run storybook
+npm run build-storybook
+```
+
+## Project Structure
+
+```
+src/
+├── index.ts              # Main entry point — Chart class (extends EventEmitter)
+├── types.ts              # All TypeScript type definitions
+├── evaluate.ts           # Orchestrates sampler selection for function evaluation
+├── datum-defaults.ts     # Default configuration for data items
+├── globals.ts            # Color palette and default dimensions
+├── utils.ts              # linspace, logspace, sgn, color utilities
+├── tip.ts                # Mouse hover tooltip system
+├── polyfills.ts          # :scope CSS selector polyfill
+├── graph-types/          # Rendering implementations
+│   ├── polyline.ts       #   Line-based graphs
+│   ├── interval.ts       #   Interval arithmetic rectangle rendering
+│   └── scatter.ts        #   Point/dot-based graphs
+├── samplers/             # Function evaluation strategies
+│   ├── builtIn.ts        #   Standard math evaluation with asymptote detection
+│   └── interval.ts       #   Interval arithmetic sampling
+├── helpers/              # Feature helpers
+│   ├── derivative.ts     #   Tangent line computation
+│   ├── secant.ts         #   Secant line calculation
+│   ├── annotations.ts    #   Vertical/horizontal reference lines
+│   └── eval.ts           #   Expression compilation and evaluation
+├── plugins/              # Plugin system
+│   └── zoom-box.ts       #   Zoom box interaction
+├── stories/              # Storybook documentation and examples
+└── evaluate.test.js      # Jest test suite
+```
+
+## Architecture
+
+- **Chart class** (`src/index.ts`): Central orchestrator. Extends EventEmitter. Manages D3 selections, scales, axes, zoom/pan, and renders data items.
+- **Samplers** (`src/samplers/`): Evaluate mathematical expressions. `builtIn` uses standard JS math; `interval` uses interval arithmetic for guaranteed correctness.
+- **Graph types** (`src/graph-types/`): Render sampled data as SVG elements (polylines, rectangles, scatter dots).
+- **Helpers** (`src/helpers/`): Compute derivative tangent lines, secant lines, and annotations.
+- **Plugins** (`src/plugins/`): Extensible behaviors (zoom-box).
+
+Data flow: `Chart.bindGraphType()` → `evaluate()` (selects sampler) → sampler produces points → graph-type renders SVG.
+
+## Code Conventions
+
+- **Module system:** ES6 import/export in source; compiled to CommonJS (`"module": "commonjs"` in tsconfig). UMD output for browsers.
+- **Formatting (Prettier):** No semicolons, single quotes, 120 char line width, no trailing commas.
+- **Indentation:** 2 spaces.
+- **Linting:** ESLint with StandardX + @typescript-eslint parser. `no-unused-vars` handled by TypeScript plugin.
+- **TypeScript:** Strict (`noImplicitAny: true`), target ES6, declarations emitted to `dist/`.
+- **Private methods:** Prefixed with underscore (e.g., `_bindNewGraphType`).
+- **D3 patterns:** Selection-based API, functional composition, method chaining.
+
+## Build System
+
+- **Webpack 4** bundles `src/index.ts` → `dist/function-plot.js` (UMD, library name `functionPlot`).
+- **ts-loader** handles TypeScript compilation in webpack.
+- **Babel 7** with preset-env and preset-typescript for transpilation.
+- **TypeDoc** generates API documentation to `site/docs/`.
+
+## Testing
+
+- **Framework:** Jest 26
+- **Config:** `jest.config.js` (rootDir: `src`)
+- **Test files:** `src/evaluate.test.js`
+- **Run:** `npm test`
+- Tests cover the evaluate function with both built-in and interval samplers.
+
+## Key Dependencies
+
+| Dependency | Purpose |
+|---|---|
+| d3-* (axis, scale, selection, shape, zoom, etc.) | Core rendering and interaction |
+| built-in-math-eval | Standard math expression evaluation |
+| interval-arithmetic-eval | Interval arithmetic for pixel-perfect bounds |
+| clamp | Value clamping utility |
+| events | EventEmitter base class |
+
+## CI
+
+- **Travis CI** runs on Node.js 12: `npm install` → `npm test` → `npm run build` → chromatic (Storybook visual testing).
+- GitHub stale bot closes issues after 90 days of inactivity (30-day warning).
+
+## Tips for Contributors
+
+- The main Chart class in `src/index.ts` is the largest file (~760 lines). Most rendering logic lives there.
+- All public types are defined in `src/types.ts` — update these when changing the API surface.
+- The `evaluate()` function in `src/evaluate.ts` selects between samplers based on `datum.sampler` field.
+- Graph types in `src/graph-types/` follow a consistent pattern: receive D3 selection + sampled data, return rendered SVG groups.