# Tech Stack

## Runtime & Language
- **Python ≥3.13** (type: runtime)
- Streamlit (type: web framework) - multi-page app: Home, Stemwijzer, Explorer (4 tabs)

## Data Layer
- **DuckDB** (type: database) - 9 tables: motions, mp_votes, svd_vectors, mp_party_history, etc.
- **ibis** (type: ORM) - DuckDB backend for Pythonic SQL
- Query mode: duckdb:// path or :memory: (see database.py:50-51)

## ML / Analytics
- **scikit-learn** (type: ML) - clustering, Procrustes alignment
- **UMAP** (type: dimensionality reduction) - 2D political compass projection
- **scipy** (type: scientific computing) - spatial/alignment algorithms
- **numpy** (type: numerical computing) - array operations

## Visualization
- **Plotly** (type: charting) - dual-layer interactive charts (scatter + annotations)

## Key Source Files
| File | Purpose |
|------|---------|
| `database.py` | MotionDatabase singleton, DuckDB connection, 9-table schema |
| `explorer.py` | Explorer page with 4 tabs (Motion, MP, Party, Evolution) |
| `explorer_helpers.py` | Pure helper functions, Plotly chart builders, coordinate computation |
| `analysis/` | SVD pipeline, UMAP projection, clustering algorithms |
| `pipeline/` | Data fetch → transform → store pipeline |
| `pages/1_🗳️_Stemwijzer.py` | Quiz page (thin wrapper) |
| `pages/2_🔍_Explorer.py` | Explorer page (thin wrapper) |
| `config.py` | Dataclass Config pattern |

## Database Tables
- `motions` - parliamentary motions with id, title, date, category
- `mp_votes` - individual MP votes on motions (1/0/-1)
- `svd_vectors` - SVD-computed political positions (entity_id, window, vector_2d)
- `mp_party_history` - MP-to-party mappings over time
- `party_centroids` - aggregated party positions
- `windows` - time period definitions
- `mp_trajectories` - MP position changes across windows
- Plus 2 additional tables (exact names vary)