docs: add gds-axelrod case study

docs/case-studies/axelrod.md

@@ -0,0 +1,79 @@
+# Axelrod Tournament
+
+**One model, many views** — an interactive exploration of Axelrod's iterated Prisoner's Dilemma tournament, built on the GDS ecosystem.
+
+[:octicons-link-external-16: Live Site](https://blockscience.github.io/gds-axelrod/)   [:octicons-mark-github-16: Source](https://github.com/BlockScience/gds-axelrod)
+
+---
+
+## Overview
+
+[gds-axelrod](https://github.com/BlockScience/gds-axelrod) demonstrates how a single OGS game specification can be projected through six distinct analytical lenses — from narrative storytelling to formal mathematical decomposition to interactive parameter exploration — without simplification or compromise.
+
+The project is a concrete realization of the **specification-as-interoperability-layer** pattern described in the [Interoperability Guide](../guides/interoperability.md): one compositional model serves as the single source of truth, and multiple independent tools consume it for different purposes.
+
+## Architecture
+
+The project splits into two tiers:
+
+```
+Pipeline (Python)                    Site (Vite/JavaScript)
+┌──────────────────────┐            ┌──────────────────────────┐
+│  OGS game definition │──export──→ │  Canvas Petri dish viz   │
+│  gds-sim population  │  (JSON)    │  Mermaid diagrams        │
+│  gds-psuu sweeps     │            │  Narrative chapters      │
+│  Nash/dominance calc  │            │  Pyodide PSUU sandbox   │
+└──────────────────────┘            └──────────────────────────┘
+```
+
+**Pipeline**: Python data generation using `gds-games`, `gds-sim`, `gds-psuu`, and `gds-viz`. Produces JSON artifacts consumed by the frontend.
+
+**Site**: Vite-based JavaScript frontend with Canvas rendering, responsive chapter navigation, and browser-side Python execution via Pyodide.
+
+## Six Showcase Views
+
+Each page presents the same underlying Prisoner's Dilemma model through a different analytical lens:
+
+| View | What It Shows | GDS Package |
+|------|---------------|-------------|
+| **Story** | Narrative chapters with interactive sandbox simulation | Strategy definitions from OGS |
+| **Formal Structure** | Canonical `h = f . g` decomposition | `GDSSpec` + `project_canonical()` |
+| **Visualizations** | Mermaid diagrams across 6 view types | `gds-viz` on `SystemIR` |
+| **Simulation** | Population trajectory tracking over generations | `gds-sim` |
+| **Nash Analysis** | Equilibria and dominance calculations | `PatternIR` from `gds-games` |
+| **PSUU** | Interactive parameter space exploration | `gds-psuu` via Pyodide |
+
+## GDS Ecosystem Integration
+
+gds-axelrod exercises four GDS packages together, demonstrating the composability of the ecosystem:
+
+- **gds-games** (`ogs`) — defines the game as an OGS pattern, compiles to `PatternIR` and `GDSSpec`
+- **gds-viz** (`gds_viz`) — renders Mermaid diagrams from the compiled `SystemIR`
+- **gds-sim** (`gds_sim`) — runs population dynamics simulation over iterated tournament rounds
+- **gds-psuu** (`gds_psuu`) — parameter sweeps compiled to WebAssembly via Pyodide for in-browser execution
+
+## Key Patterns Demonstrated
+
+### Specification as Single Source of Truth
+
+The OGS game definition is written once. Every view — visualization, simulation, equilibrium analysis, parameter exploration — derives from the same specification. No view has a private copy of the model.
+
+### Thin Projections
+
+Each analytical tool is a thin projection over the specification:
+
+- `PatternIR` → Nash equilibria via Nashpy
+- `PatternIR` → payoff matrix → tournament simulation
+- `SystemIR` → Mermaid diagrams via gds-viz
+- `GDSSpec` → canonical decomposition
+
+### Browser-Side Computation
+
+The PSUU page compiles Python (gds-sim + gds-psuu) to WebAssembly via Pyodide, enabling interactive parameter exploration without a backend server.
+
+## Related
+
+- [Interoperability Guide](../guides/interoperability.md) — the specification-as-interoperability-layer pattern
+- [Evolution of Trust](../examples/examples/evolution-of-trust.md) — the in-repo tutorial model that gds-axelrod builds upon
+- [Prisoner's Dilemma](../examples/examples/prisoners-dilemma.md) — the base GDS framework version
+- [View Stratification](../guides/view-stratification.md) — the theoretical basis for "one model, many views"

docs/case-studies/index.md

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+# Case Studies
+
+Real-world projects built on the GDS ecosystem, demonstrating how compositional specifications translate into interactive applications, research tools, and educational platforms.
+
+| Project | Domain | GDS Packages Used | Description |
+|---------|--------|-------------------|-------------|
+| **[Axelrod Tournament](axelrod.md)** | Game Theory | gds-games, gds-sim, gds-psuu, gds-viz | Interactive exploration of the iterated Prisoner's Dilemma through six analytical views |

mkdocs.yml

@@ -114,6 +114,9 @@ plugins:
           - {psuu/getting-started.md: "Installation + first parameter sweep"}
           - psuu/guide/*.md
           - psuu/api/*.md
+        Case Studies:
+          - {case-studies/index.md: "Real-world projects built on the GDS ecosystem"}
+          - {case-studies/axelrod.md: "Axelrod tournament — one model, many views with gds-games, gds-sim, gds-psuu, gds-viz"}
         Ecosystem:
           - {framework/ecosystem.md: "All packages, their imports, and dependency relationships"}
 
@@ -332,6 +335,9 @@ nav:
               - gds_psuu.optimizers: psuu/api/optimizers.md
               - gds_psuu.sweep: psuu/api/sweep.md
               - gds_psuu.results: psuu/api/results.md
+  - Case Studies:
+      - case-studies/index.md
+      - Axelrod Tournament: case-studies/axelrod.md
   - Design & Research:
       - Layer 0 Milestone: guides/architecture-milestone-layer0.md
       - DSL Roadmap: guides/dsl-roadmap.md