# Drive Between the Lines — Phase 0 prototype

Endless driving survival game. This is the **Phase 0** skeleton from the roadmap:
a drivable car on a flat plate with scattered obstacles, plus the persistent wear
system that makes condition felt through the wheel.

## Running

```bash
npm run dev
```

Then open http://localhost:5173. Append `?seed=anything` to regenerate the world —
seeds may be numbers or words.

| | |
|---|---|
| `W` / `S` | throttle / brake-reverse |
| `A` / `D` | steer |
| `Space` | handbrake (rear wheels only) |
| `R` | respawn the car — **does not** repair it |

```bash
npm test        # sim + headless physics
npm run build   # typecheck + production bundle
```

## Layout

The one rule worth keeping: **`src/sim/` imports neither three.js nor Rapier.**
Phases 1–4 (heat, regions, front lines, quests) are all simulation, and keeping
them engine-free is what makes them unit-testable and fast-forwardable — you can
run a hundred simulated days in milliseconds to tune an escalation curve without
ever opening a browser.

```
src/
  sim/        pure model — world generation, car condition → handling
  physics/    Rapier world, raycast vehicle, input → wheel forces
  render/     three.js scene, chase camera
  core/       fixed-timestep loop, seeded RNG, keyboard
  ui/         debug HUD
  carSpec.ts  shared car dimensions, so body and mesh cannot drift apart
```

Data flows one way: `sim` → `physics` → `render`. Condition reaches the physics
layer already digested into a `Handling` by `deriveHandling`, so there is exactly
one place where "how broken the car is" turns into "how it drives".

## Notes on the state of it

- **The car handles like a placeholder.** Suspension, grip, and engine numbers in
  `physics/physics.ts` and `sim/car.ts` are first guesses that pass a smoke test,
  not something tuned by feel. That tuning *is* Phase 0's verification gate.
- **Wear rates are deliberately aggressive** so decline is visible in minutes
  rather than hours. Turn them down in `applyWear` once the curve reads right.
- **No interpolation** between physics steps. Fine at 60 Hz; revisit if the step
  rate changes.
- **Condition is not yet persisted** across reloads. IndexedDB comes with the
  campaign layer.
- **Bundle:** ~2.7 MB raw / ~945 KB gzipped, dominated by Rapier's WASM, which
  `rapier3d-compat` inlines as base64. Switching to the non-compat `@dimforge/rapier3d`
  package serves the WASM as a separate file (~570 KB gzipped, compiled in
  parallel with the JS) at the cost of extra Vite plugin config. Worth doing
  before anyone but you plays it; not worth doing now.

## Next

Phase 0's gate: drive for 15–20 minutes, feel the condition changing how the car
handles, and want to keep driving anyway. Everything else waits on that.