# TOW — trailer reversing trainer

A small browser game that teaches you the counter-intuitive art of **reversing a
car with a trailer**. Vector / "Tron" graphics, no build step, no dependencies.

## Play

Just open the file in Safari:

```sh
open index.html
```

(or double-click `index.html`). Everything runs client-side from `file://` — the
scripts are plain classic `<script>` tags specifically so this works without a
server.

If you'd rather serve it over HTTP:

```sh
python3 -m http.server 8000   # then visit http://localhost:8000
```

## How to play

- **W / S** — drive forward / reverse (gear shows **D** / **R** / **N**).
- **A / D** — steer. You must *hold* the key to wind the wheel over; it
  self-centers when you let go. Watch the steering-wheel instrument.
- **R** — reset the current map · **N** — next map · **1–5** — jump to a map.

Goal: back the **trailer** into the dashed green zone, roughly aligned with the
arrow, and come to a stop. The **RIG ANGLE** panel (bottom-left) shows the live
angle between car and trailer — keep an eye on it: reversing amplifies the angle,
and if it folds past the limit you'll **jackknife** (ease off the steering and
pull forward to straighten out).

### Maps

1. **Loading Dock** — straight reverse, the warm-up.
2. **Parking Lot** — 90° back-in between two cars.
3. **Roadside** — parallel park into a gap at the curb.
4. **Driveway** — back up an angled drive between the house and a hedge.
5. **Random** — a procedurally generated lot or roadside scenario, rebuilt every
   time you arrive at it (each candidate is validated for a collision-free,
   reachable start before being accepted). `R` retries the same layout.

## Code layout

Plain ES5-ish modules attached to a global `TOW` namespace, loaded in order:

| File              | Responsibility                                                   |
|-------------------|-----------------------------------------------------------------|
| `js/physics.js`   | Vehicle kinematics (bicycle model + trailer articulation), geometry, OBB/SAT collision. |
| `js/maps.js`      | Scenario data: start pose, goal zone, obstacles.                |
| `js/input.js`     | Keyboard state and one-shot actions.                            |
| `js/render.js`    | Tron-style scene drawing.                                       |
| `js/hud.js`       | Steering wheel + rig-angle schematic + gear/speed instruments.  |
| `js/game.js`      | Main loop, collision handling, win detection, map switching.    |

The physics reference point is the car's **rear axle**. The trailer follows the
standard articulation equation, which is what makes reversing behave like the
real thing.