Document city traffic; refresh street screenshots

README.md

@@ -16,7 +16,7 @@ indexing API and the browser frontend (plain ES modules and WebGL2, no build ste
 | ![2D map](docs/images/map-2d.png) | **2D map**: a squarified treemap of every file, sized by lines or references, with source code rendered right on the tiles as you zoom in. |
 | ![3D landscape](docs/images/landscape-3d.png) | **3D landscape**: the same map extruded, orbit, pan and dolly around it. |
 | ![Routes in the city](docs/images/city-routes.png) | **City**: folders become districts and blocks, files become buildings (footprint from lines, height from complexity, lit windows from definitions). Select a file to see its imports as cyan routes and its dependents as pulsing magenta routes along the streets. |
-| ![Walking the city](docs/images/city-walk.png) | **Walk and fly** at street level past lit doorways, streetlights, bins, benches and trees, with signs on every wall, folder street signs on the corners, source code on the facade in front of you, wandering residents and a city wall covered in posters. |
+| ![Walking the city](docs/images/city-walk.png) | **Walk and fly** at street level past lit doorways, passing traffic, streetlights, bins, benches and trees, with signs on every wall, folder street signs on the corners, source code on the facade in front of you, wandering residents and a city wall covered in posters. |
 
 Also:
 

docs/ARCHITECTURE.md

@@ -80,7 +80,9 @@ Plain ES modules, no framework, no build step.
 3. **Doors and street furniture:** small instanced boxes (lit doorways, lamp posts and heads, bins,
    benches, trees, hydrants, post boxes) drawn with a separate shader variant, and only within a few
    hundred metres of the camera. Streetlights stand on folder boundaries, and everything sits on
-   folder pavements, never the road.
+   folder pavements, never the road. Cars use the same shader: each block inside a folder has a
+   one-lane loop half-way into the street around it, and only cars near the camera are rebuilt
+   each frame.
 4. **Effects:** additive and never occluding. Lamp light pools, search beacons, fire and smoke particles (stateless,
    animated in the vertex shader), residents (procedural stick-figure sprites), street routes
    (mitred ribbons with chevrons or pulsing dashes, kept in right-hand lanes) and import arcs.

docs/CITY.md

@@ -24,6 +24,7 @@ scale, so a large repository is a large city.
 | **Lit doorway** | The building's door: facing the street, or a back door onto an alley for files in the middle of a folder |
 | **Streetlights** with pools of light | The edges of each folder: lights stand on its boundary, at every corner and every 20 m or so |
 | **Bins, benches, trees, hydrants, post boxes** | Street furniture on the folder's pavement. Purely for atmosphere |
+| **Cars** | Traffic circling the blocks inside each folder, on its grey streets (never on the black ground between districts). They drive on the right and stop for you if you stand in their lane. Purely for atmosphere |
 | **Cyan chevrons** on the road | Route to a file the selected file imports (**amber** if the import was inferred) |
 | **Pulsing magenta dashes** on the road | Route from a file that imports the selected file |
 | **Arcs** in the sky | The same import relationships, as the crow flies |