docs: PR-B physics, scoreboard, team1/2, multi-client UX

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

README.md

@@ -1,6 +1,6 @@
 ## curltastic
 
-A multiplayer 2D curling game for mobile browser. Any number of clients can join a room, pick Red or Yellow freely, and throw when it is that team's turn (solo pass-and-play or remote opponents).
+A multiplayer 2D curling game for mobile browser. Any number of clients can join a room, pick **Team 1** or **Team 2** freely, and throw when it is that team's turn (solo pass-and-play or remote opponents). Default palette: Team 1 red, Team 2 yellow.
 
 - **Backend** — Rust, Axum, WebSocket, Rapier2D physics (server-authoritative, 120 Hz).
 - **Frontend** — TypeScript, Vite, Canvas2D, portrait-first touch UI.
@@ -25,45 +25,59 @@ A multiplayer 2D curling game for mobile browser. Any number of clients can join
    ```
    http://localhost:5173/?room=DEMO1
    ```
-   Use the team dropdown in the top-right to switch between Red and Yellow — this enables local pass-and-play on one device. Use the *Copy share link* button to invite an opponent on another device.
+   Use the team dropdown to switch between Team 1 and Team 2 anytime. Use *Copy share link* to invite another device.
-
-### Mobile devices
-
-The frontend binds to `0.0.0.0` via `--host`. Find your machine's LAN IP and open `http://<ip>:5173/?room=CODE` on the phone. Both devices must be on the same Wi-Fi and able to reach the backend on port `3000`. The default view is zoomed in on the house; drag the sheet vertically to scroll up to the hog line.
 
 ### Controls
 
-- When it is your team's turn, drag on the sheet to place the broom (aim point) — aim is not limited to the house.
+- On your team's turn, drag on solid ice to place the broom (aim is **not** limited to the house).
-- When it is not your turn, drag to pan the ice (default framing shows the house with sidelines; pan up toward the hog line).
+- Otherwise, drag to pan (default framing shows house + sidelines; pan up toward the hog line).
-- Use the team dropdown to choose which team's stone you are throwing; switch any time (including mid-end for solo play).
+- Team dropdown: free switch mid-game (solo: throw for Team 1, switch, throw for Team 2).
-- Use the left/right curl buttons and the weight/friction controls; friction is a local scalar.
+- Velocity slider (release speed, m/s), curl buttons, friction scalar **0.5–1.5** (local; multiplies ice µ(v) table).
-- Tap **THROW**. Anyone identifying as the turn team may throw.
+- Tap **THROW**. Anyone joined as the current turn team may throw.
-- The server runs physics for every stone and streams multi-stone paths; the client animates them on one clock so collisions move together.
+- Parallel multi-stone trajectories; rotation θ comes from physics.
+- Skeuomorphic 2×8 stones-left HUD; end-of-end modal with scoreboard (auto ~5s + manual dismiss).
 
-### Architecture
+### Physics (high level)
 
-- WebSocket JSON protocol with tagged messages.
+- Pure initial **velocity** (m/s), not discrete weight.
-- Server simulates each throw at 120 Hz and sends a subset of `(x, y, t)` path points at 40 Hz.
+- Ice friction µ(v) table (interpolated) × local scalar; linear and angular damping share the table.
-- All game state, scoring, end management, and hammer rules live on the server.
+- Curl: initial |ω| = 5 rot / 14 s; lateral speed ≈ k / v_forward (clockwise → right).
-- Disconnects are tolerated: the room and turn remain in memory.
+- Back line and sidelines are **not** colliders — touch → out of play after sim.
+- Stone ids: `{ team, n }` with n = 1…8 per team per end.
+- Foot-derived radii use `FEET_TO_METERS = 0.3048`.
+
+### Architecture / protocol
+
+- WebSocket JSON, snake_case tags.
+- `game_state` includes totals, hammer, turn_team, **scoreboard** (per end: hammer, team1 pts, team2 pts), **stones_remaining**, stones.
+- `trajectories` message: `{ stones: [{ stone_id, rotation, team, trajectory: [[x,y,theta], ...] }] }` sampled at 40 Hz from 120 Hz sim (`t = index / 40`).
+- No room-full limit; no `end_scored` message (scoreboard replaces it).
 
 ### E2E tests
 
-With the backend and frontend dev server running:
+With the backend running (`cargo run --release` on :3000):
 
 ```bash
 cd e2e
-npm install -g ws   # or npm install ws locally in the project
+npm install -g ws   # or npm install ws
-node e2e_test.cjs              # room lifecycle, throw, trajectory
+node e2e_test.cjs
-node e2e_score.cjs             # alternate turns / stones in play
+node e2e_score.cjs
-node e2e_persistence.cjs       # multi-throw stone persistence
+node e2e_persistence.cjs
-node e2e_multi_client.cjs      # 3 clients share state (no room-full)
+node e2e_multi_client.cjs
-node e2e_end_score.cjs         # full end → end_scored + next end
+node e2e_end_score.cjs          # full end → scoreboard entry + next end
-node collision_trajectory_qa.cjs  # multi-stone trajectory on collision
+node collision_trajectory_qa.cjs
+node load_test.cjs              # optional concurrent rooms
 ```
 
-### Limitations / known simplifications
+Unit tests: `cd backend && cargo test`, `cd frontend && npm test`.
+
+### Branches (this work)
+
+- **`jasonlooked`** — PR-A refactor: multi-client, multi-path animation, free broom, camera, FEET_TO_METERS.
+- **`pr2-features`** — PR-B features: physics rewrite, team1/2 wire, scoreboard, HUD, modal (branched from PR-A tip).
+
+### Limitations
 
 - No accounts, persistence, anti-cheat, replay log, or turn timer.
-- Curl is fixed as a function of release speed (more curl at lower speed); sweeping is not implemented.
+- Sweeping not implemented; friction/curl not shared-room state.
-- Stones that pass the back line or leave the sheet are removed from play.
+- Stones past back/sideline/hog rules are removed from play after simulation.