# Stacktower

> Stacktower is a free tool that visualizes software dependency graphs as physical towers, inspired by XKCD #2347. Try it in the browser at https://app.stacktower.io — type any package name from npm, PyPI, crates.io, Go modules, Maven, Composer, or RubyGems and get its dependency tower instantly.

## About

The blog post at https://stacktower.io documents the journey of building Stacktower - a visualization tool that transforms dependency graphs into stacked tower diagrams. Instead of traditional node-link diagrams with arrows, dependencies are represented as physical blocks where blocks rest on what they depend on.

## Try It

- Web app (no install required): https://app.stacktower.io
- View a specific package, e.g. FastAPI: https://app.stacktower.io/package/python/fastapi
- CLI (open source, written in Go): https://github.com/stacktower-io/stacktower

## Key Topics

- **Dependency Visualization**: A new approach to visualizing software dependencies as physical structures
- **Graph Algorithms**: Layered graph drawing, crossing minimization, NP-hard optimization
- **PQ-Trees**: Data structure for encoding permutation constraints efficiently
- **Barycenter Heuristic**: Fast approximation algorithm for node ordering
- **Branch and Bound**: Combining exact and heuristic methods for optimal layouts

## Sections

- The Spark: Origin story inspired by XKCD comic #2347
- Welcome to the Side Quest: Discovery of the underlying NP-hard problem
- Finding a Battle Plan: Research into existing algorithms (Sugiyama Framework)
- Reducing the Problem: Graph transformations to make stacking possible
- The Evolution of an Algorithm: From brute force to PQ-trees to heuristics
- The Final Touches: Implementation details and rendering

## Technical Details

The tool is implemented in Go and supports:
- npm (JavaScript packages)
- PyPI (Python packages)
- crates.io (Rust packages)
- Go modules
- Maven (Java packages)
- Packagist/Composer (PHP packages)
- RubyGems (Ruby packages)
- GitHub and GitLab repositories

It fetches dependency data from package registries and maintainer information from GitHub.

## Links

- Web App: https://app.stacktower.io
- Source Code: https://github.com/stacktower-io/stacktower
- Author: Matthias Huels (https://huels.ai)
- Original Inspiration: XKCD #2347 (https://xkcd.com/2347/)