The user wants me to build a single-page web app in index.html that:
1. Uses d3.min.js (already present in /tmp/ws)
2. Renders a force-directed graph with ~40 nodes in clusters
3. Draggable nodes
4. Hover highlighting of neighbors
5. Zoom/pan
6. All inline CSS and JS
7. No external resources

Let me first check that d3.min.js exists in the current directory.

The user wants me to build a single-page web app with an interactive force-directed graph using d3.min.js. The requirements are:

1. All in one file (index.html)
2. No external resources, just d3.min.js from the local directory
3. About 40 nodes in several clusters
4. Draggable nodes
5. Hover highlighting of neighbors
6. Zoom/pan capability
7. Sample nodes and links defined inline

I need to:
1. Load d3.min.js with `<script src="d3.min.js"></script>`
2. Create inline CSS in `<style>`
3. Create inline JS in `<script>`
4. Generate ~40 nodes in clusters with links
5. Implement force simulation
6. Add drag behavior
7. Add hover highlighting
8. Add zoom/pan

Let me design the clusters and data generation, then build the visualization.

Plan:
- Create 5 clusters with ~8 nodes each (total ~40 nodes)
- Generate links within clusters (dense) and between clusters (sparse)
- Use d3.forceSimulation with forceManyBody, forceCenter, forceLink, forceCollide
- Implement drag behavior
- Implement hover highlighting (highlight node and neighbors on hover)
- Implement zoom/pan with d3.zoom

Let me write this out. I'll create a well-structured, visually appealing force-directed graph.

The user asked me to build a single-page web app with D3.js. I've already written the index.html file. Let me verify it's present and complete.

The file has been successfully created. Let me verify the content is correct and the script tag properly references d3.min.js.